CN111636987A

CN111636987A - Pressure limiting valve

Info

Publication number: CN111636987A
Application number: CN202010495671.5A
Authority: CN
Inventors: 苏晓东; 王红磊; 唐继响; 何浩然
Original assignee: FAW Jiefang Automotive Co Ltd
Current assignee: FAW Jiefang Automotive Co Ltd
Priority date: 2020-06-03
Filing date: 2020-06-03
Publication date: 2020-09-08

Abstract

The invention relates to the technical field of high-pressure common rail systems of diesel engines, and particularly discloses a pressure limiting valve, which comprises: the valve seat is provided with an oil drainage hole; the outer valve core is arranged on the valve seat in a sliding mode and is provided with an inner accommodating cavity and a pressure reducing oil hole; the valve comprises a shell and a spring, wherein one end of the spring is abutted against the shell, and the other end of the spring is abutted against an outer valve core; the inner valve core is arranged in the inner accommodating cavity, one end of the inner valve core can be spaced from the oil outlet end of the pressure reducing oil hole, and the other end of the inner valve core can be abutted against the outer shell; the outer valve core can be located at the sealing position for sealing the oil drain hole and the opening position for opening the oil drain hole under the combined action of the acting force of the spring, the fuel pressure in the inner containing cavity and the fuel pressure of the common rail system. When the maximum pressure of the common rail system is increased, the diameter of an oil drainage hole of a valve seat does not need to be reduced, the rigidity of a spring does not need to be increased, and the sensitivity of the elastic force of the spring to the compression amount of the spring can be reduced.

Description

Pressure limiting valve

Technical Field

The invention relates to the technical field of high-pressure common rail systems of diesel engines, in particular to a pressure limiting valve.

Background

In order to ensure safety, a pressure limiting valve is generally arranged in a high-pressure pipeline of the high-pressure common rail system to ensure that the pressure limiting valve is opened when the high-pressure common rail system fails and the pressure abnormally rises, so that the pressure is not increased or is reduced, and the safety of the high-pressure common rail system is ensured. As emission and fuel consumption regulations become more stringent, the high pressure common rail system of the diesel engine must have a higher operating pressure.

As shown in fig. 1, in the prior art, a pressure limiting valve includes an outer valve core 20 and a valve seat 10, the valve seat 10 is provided with a stepped hole, and the outer valve core 20 is disposed in the stepped hole and can abut against a step of the stepped hole to seal the stepped hole. The outer spool 20 is set on the valve seat 10 by the outer spool 20 by the spring force F. A sealing line with the diameter phi D is formed between the outer valve core 20 and the valve seat 10, and the sealing diameter is generally 1mm-1.5 mm. In the high-pressure common rail system, when the product of the high-pressure fuel pressure p and the area enclosed by the sealing line is smaller than the upper spring force F, namely p pi/4D²< F, the outer spool 20 does not move and the high pressure fuel is sealed. With increasing p, when p is pi/4D²If the pressure is higher than F, the outer valve core 20 overcomes the spring force to move in the opposite direction under the action of oil pressure, and the fuel will flow out from the side gap between the valve seat 10 and the outer valve core 20. The pressure limiting valve is opened, fuel oil flows out, and the pressure of the system is reduced.

As the maximum working pressure of the common rail system is constantly increased, the opening pressure of the pressure limiting valve must also be increased. In the prior art, two methods are used for improving the opening pressure of the pressure limiting valve, wherein the first method is to reduce the size of an oil drainage hole 101 of a valve seat 10 so as to reduce the sealing area; another is to increase the spring force. However, due to the limitations of machining capability, and the requirement for drainage flow, the diameter of the drainage hole 101 cannot be made very small, and therefore the cracking pressure can only be increased by the second method. If the spring force is increased by simply increasing the compression of the spring, the shear stress of the spring is increased or the problem of doubling up is caused. Therefore, it is necessary to increase the spring force by increasing the spring rate to control a reasonable amount of compression. The diameter of the sealing line of the pressure limiting valve is small, the rigidity of the spring is improved, so that the elasticity of the spring is more sensitive to the compression amount, and the tiny change of the compression amount can result in a large opening pressure change range, which causes adverse effect on the pressure control of the high-pressure common rail system.

Disclosure of Invention

The invention aims to provide a pressure limiting valve, so that when the maximum pressure of a common rail system is increased, the diameter of an oil drainage hole of a valve seat does not need to be reduced, the rigidity of a spring does not need to be increased, and even the rigidity of the spring can be reduced, so that the sensitivity of the elastic force of the spring to the compression amount of the spring is reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a pressure limiting valve comprising:

the valve seat is provided with an oil drainage hole and is abutted against the common rail system;

the outer valve core is arranged on the valve seat in a sliding mode, an inner accommodating cavity and a pressure reducing oil hole which are communicated are formed in the outer valve core, and fuel oil of the common rail system can flow into the inner accommodating cavity from the pressure reducing oil hole;

the valve comprises a shell and a spring, wherein one end of the spring is abutted against the shell, and the other end of the spring is abutted against the outer valve core;

the inner valve core is arranged in the inner accommodating cavity, one end of the inner valve core can be spaced from the oil outlet end of the pressure reducing oil hole, and the other end of the inner valve core can be abutted against the shell;

the outer valve core can be in a sealing position for sealing the oil drainage hole and an opening position for opening the oil drainage hole under the combined action of the acting force of the spring, the fuel pressure in the inner containing cavity and the fuel pressure of the common rail system.

Preferably, the outer valve body can abut against an inner wall of the oil release hole and form a seal line, and a cross-sectional area of the inner accommodating chamber is larger than a cross-sectional area of the relief oil hole and smaller than a seal area defined by the seal line.

Preferably, a gap is formed between the inner valve core and the inner wall of the inner accommodating cavity.

Preferably, the valve seat is further provided with an oil return hole, and the oil return hole is used for discharging fuel oil flowing out from the oil drainage hole and the gap.

Preferably, the valve seat is further provided with an outer accommodating cavity, the outer accommodating cavity is communicated with the oil drainage hole and is located at the oil outlet end of the oil drainage hole, and the outer valve core is arranged in the outer accommodating cavity in a sliding mode.

Preferably, the pressure limiting valve further comprises a guide sleeve, the guide sleeve is arranged in the outer containing cavity, and the outer valve core is arranged in the guide sleeve in a sliding penetrating mode.

Preferably, the pressure limiting valve further comprises a pressure regulating gasket, and the pressure regulating gasket is located between the spring and the outer valve core.

Preferably, the pressure regulating gasket is provided with a step hole, the other end of the outer valve core abuts against a step surface of the step hole, and the inner valve core penetrates through the step hole and abuts against the outer shell.

Preferably, the shell is provided with an avoiding groove, and the pressure regulating gasket is arranged in the avoiding groove.

Preferably, the housing is provided with an annular guide groove, and the spring is arranged in the annular guide groove.

The invention has the beneficial effects that:

the outer valve core is simultaneously subjected to acting forces of three aspects, firstly, the outer valve core is pressed on the valve seat under the action of the elastic force F of the spring and is abutted against the inner wall of the oil drainage hole; secondly, the outer valve core is subjected to the hydraulic pressure F1up of the fuel in the common rail system to enable the outer valve core to be far away from the valve seat; third, the outer spool receives the hydraulic pressure F1down of the fuel in the outer receiving chamber, and therefore the resultant force F1 of the fuel received in the common rail system is F1up-F1 down. When the elasticity F of the spring is greater than Fl, the outer valve core is in a sealing position, the oil drainage hole is sealed, and fuel cannot flow out of the oil drainage hole. Along with the continuous rising of fuel pressure p, when F < Fl, outer valve core is pushed by hydraulic pressure and is upwards removed, and the fuel flows out from the draining hole, and fuel pressure p descends to play the pressure restriction effect.

The fuel oil in the inner containing cavity applies downward acting force F1down to the outer valve core, so that the resultant force F of the high-pressure fuel oil acting on the outer valve core is reduced, the rigidity of the spring is not required to be improved or even reduced when the pressure of the common rail system is improved, the sensitivity of the elastic force to the compression amount of the spring is reduced, and the opening pressure of the pressure limiting valve is conveniently and accurately controlled.

The pressure limiting valve provided by the embodiment does not need to reduce the hydraulic pressure F1up of fuel oil in the common rail system of the outer valve core by changing the size of the oil drainage hole of the valve seat, so that the processing difficulty of each part of the pressure relief valve can be reduced, the processing precision is improved, and the pressure limiting valve is ensured to have a better sealing effect.

Drawings

FIG. 1 is a cross-sectional view of a prior art pressure limiting valve;

FIG. 2 is a cross-sectional view of a pressure limiting valve and common rail system provided by an embodiment of the present invention;

FIG. 3 is a cross-sectional view of an outer spool and guide sleeve provided by an embodiment of the present invention;

fig. 4 is a cross-sectional view of an outer spool and an inner spool provided by an embodiment of the present invention.

In the figure:

10. a valve seat; 101. an oil drainage hole; 20. a valve core;

1. a valve seat; 11. an oil drainage hole; 12. an outer receiving cavity; 13. an oil return hole;

2. an outer valve core; 21. a relief oil hole; 22. an inner accommodating cavity;

3. an inner valve core; 4. a guide sleeve; 5. a pressure regulating gasket; 6. a spring;

7. a housing; 71. an avoidance groove; 72. a limiting boss; 73. an annular guide groove;

100. a common rail system; p, fuel pressure.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the elements associated with the present invention are shown in the drawings.

In the present invention, the directional terms such as "upper", "lower", "left", "right", "inner" and "outer" are used for easy understanding without making a contrary explanation, and thus do not limit the scope of the present invention.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The embodiment provides a pressure limiting valve, which is used for limiting the pressure of the common rail system 100 and preventing the fuel pressure in the common rail system 100 from exceeding a preset value, but is not limited to the above, and can also be used for other systems needing pressure limiting, so that when the maximum pressure of the common rail system 100 is increased, the diameter of the oil drainage hole 11 of the valve seat 1 does not need to be reduced, the rigidity of the spring 6 does not need to be increased, and even the sensitivity of the elastic force of the spring 6 to the compression amount of the spring 6 can be reduced.

As shown in fig. 2, the pressure limiting valve provided in the present embodiment includes a valve seat 1, an outer spool 2, an inner spool 3, a housing 7, and a spring 6. The valve seat 1 is provided with an oil drainage hole 11, and the valve seat 1 is abutted to the common rail system 100. The upper end of the spring 6 abuts against the housing 7, and the lower end of the spring 6 abuts against the outer valve element 2. The outer valve core 2 is arranged on the valve seat 1 in a sliding mode, the outer valve core 2 is provided with an inner accommodating cavity 22 and a pressure reducing oil hole 21 which are communicated, and fuel oil of the common rail system 100 can flow into the inner accommodating cavity 22 from the pressure reducing oil hole 21.

The inner valve core 3 is disposed in the inner accommodating cavity 22, and a distance can be set between the lower end of the inner valve core 3 and the oil outlet end of the pressure reducing oil hole 21, so that the fuel in the inner accommodating cavity 22 applies a downward acting force to the outer valve core 2 (it can be understood that the upper and lower directions in this embodiment are illustrated by taking fig. 2 as an example, for convenience of description, and when the placement direction of the pressure limiting valve changes, the upper and lower directions in this embodiment also change, and therefore, the upper and lower directions in this embodiment do not limit the protection scope of the present invention). The upper end of the inner spool 3 can abut against the outer case 7, so that the upward force of the fuel in the inner accommodating chamber 22 acting on the inner spool 3 can be transmitted to the outer case 7 without acting on the outer spool 2. It can be understood that the internal receiving chamber 22 communicates with the common rail system 100 through the pressure reducing oil hole 21, and thus the fuel pressure P in the internal receiving chamber 22 is equal to the fuel pressure P in the common rail system 100.

The outer spool 2 can be brought into a sealing position for sealing the drain hole 11 and an opening position for opening the drain hole 11 by the combined action of the urging force of the spring 6, the fuel pressure in the inner accommodating chamber 22, and the fuel pressure of the common rail system 100.

The outer valve core 2 is simultaneously applied with three acting forces, firstly, the outer valve core 2 is pressed on the valve seat 1 under the action of the elastic force F of the spring 6 and is abutted against the inner wall of the oil drainage hole 11; secondly, the outer valve core 2 is subjected to the hydraulic pressure F1up of the fuel in the common rail system 100, so that the outer valve core 2 is far away from the valve seat 1; third, the outer spool 2 receives the hydraulic pressure F1down of the fuel in the outer receiving chamber 12, and therefore the resultant force F1 of the fuel received in the common rail system 100 by the outer spool 2 becomes F1up-F1 down. When the elastic force F of the spring 6 is greater than Fl, the outer valve element 2 is in a sealing position, the oil drainage hole 11 is sealed, and fuel cannot flow out of the oil drainage hole 11. Along with the continuous rising of fuel pressure p, when F < Fl, outer case 2 is pushed by hydraulic pressure and is upwards moved, and the fuel flows out from draining hole 11, and fuel pressure p descends to play the pressure restriction effect.

The fuel in the inner accommodating cavity 22 exerts downward acting force F1down on the outer valve core 2, so that the resultant force F of the high-pressure fuel acting on the outer valve core 2 is reduced, the rigidity of the spring 6 is not required to be improved or even reduced when the pressure of the common rail system 100 is improved, the sensitivity of the elastic force to the compression amount of the spring 6 is reduced, and the opening pressure of the pressure limiting valve is conveniently and accurately controlled.

Referring to fig. 1, the pressure limiting valve provided in this embodiment does not need to reduce the hydraulic pressure F1up of the fuel in the common rail system 100 on the outer valve core 2 by changing the size of the oil drainage hole 101 of the valve seat 10, so that the processing difficulty of each part of the pressure relief valve can be reduced, the processing precision is improved, and the pressure limiting valve is ensured to have a better sealing effect.

Specifically, the outer spool 2 can abut against the inner wall of the oil release hole 11, and form a seal line that encloses the seal area S1. The cross-sectional area of the inner accommodating chamber 22 is larger than that of the relief oil hole 21 and smaller than the sealing area S1. It will be appreciated that the sealing area S1 is the area of the cross section where the inner wall of the drain hole 11 abuts the outer valve element 2.

The outer spool 2 is pressed against the valve seat 1 by the spring force F of the spring 6. The sealing area is S1, and the cross-sectional area of the pressure reducing oil hole 21 is S2, so that the hydraulic pressure Flup of the fuel in the common rail system 100 applied to the outer valve element 2 is (S1-S2). The cross-sectional area of the inner accommodating chamber 22 is S3, and the outer spool 2 receives the downward hydraulic force F1down of the fuel in the inner accommodating chamber 22 (S3-S2) × p, so that the hydraulic force acting on the outer spool 2 is partially balanced, and finally the resultant force Fl on the outer spool 2 is (S1-S3) × p. Therefore, the opening pressure of the pressure relief valve can be kept unchanged by increasing the cross-sectional area S1 of the joint of the oil drainage hole 11 and the outer valve element 2 and the cross-sectional area S3 of the inner accommodating cavity 22, so that the processing difficulty of each part of the pressure relief valve is reduced, the processing precision is improved, and the pressure relief valve is ensured to have a better sealing effect.

Preferably, for the sealed effect when improving outer case 2 sealed draining hole 11, outer case 2 includes cylinder portion and the circular cone portion that sets up from top to bottom, and the circular cone portion can partly stretch into draining hole 11, and the periphery of circular cone portion can butt the upper end of draining hole 11 to shutoff draining hole 11. Preferably, the lower end of the cylindrical portion has a space from the lower cavity wall of the outer receiving cavity 12 to ensure that the outer peripheral surface of the conical portion abuts against the upper end of the oil release hole 11 and that the outer receiving cavity 12 can receive a part of the fuel. The inner accommodating cavity 22 is coaxial with the outer valve core 2, and the inner valve core 3 is of a cylindrical structure and is arranged in the inner accommodating cavity 22.

For making outer case 2 slide for disk seat 1 steadily, still seted up outer chamber 12 that holds on the disk seat 1, hold chamber 12 and draining hole 11 intercommunication outward, and be located the play oil end of draining hole 11, outer case 2 slides and sets up in holding chamber 12 outward.

In order to install the outer valve core 2 conveniently, the pressure limiting valve can further comprise a guide sleeve 4, the guide sleeve 4 is arranged in the outer containing cavity 12, and the outer valve core 2 penetrates through the guide sleeve 4 in a sliding mode. The guide sleeve 4 and the valve seat 1 can be of a split structure or an integrated structure.

As shown in fig. 3, in order to make the fuel flowing into the outer accommodating chamber 12 from the drain hole 11 flow out, the cross section of the outer valve core 2 is preferably a waist-shaped structure, and the outer periphery of the outer valve core 2 of the structure has a circular arc structure at the same time, so that the outer valve core can be matched with the guide sleeve 4 to ensure the stability of sliding.

As shown in fig. 2, preferably, the valve seat 1 further has an oil return hole 13, and the oil return hole 13 is used for discharging the fuel flowing out from the oil drain hole 11 and/or the gap, and further discharging the fuel in the pressure limiting valve. In the present embodiment, the axis of the oil return hole 13 is parallel to the axis of the oil release hole 11, and is disposed through the valve seat 1.

With the increasing pressure of the common rail system 100, in order to improve the fuel supply efficiency of the common rail system 100 and reduce the loss, the current design of the fuel injector is a static leakage-free structure. The pressure limiting valve in the prior art is linear sealing, has better sealing performance under high pressure and basically has no leakage. Therefore, in the case of no fuel injection from the injectors, the high pressure in the common rail system 100 cannot be reduced due to the high pressure tightness. This may result in the common rail system 100 failing to drop in pressure after the injector suddenly stops injecting fuel. When the injection is restarted, the common rail system 100 pressure cannot drop to the desired target pressure, thereby causing the diesel engine to operate unstably. Or after the fuel injector stops injecting fuel, when the common rail system 100 needs to be disassembled and repaired, the pressure of the common rail system 100 cannot be reduced, and certain risk is caused to disassembly. As shown in fig. 2 and 4, the inner core 3 is preferably provided with a clearance from the inner wall of the inner receiving chamber 22. Through setting up reasonable clearance size, can guarantee to have certain high-pressure fuel to leak, let out leakage quantity simultaneously and can control at reasonable within range to can be so that when rail system 100 stop work, pressure can descend very fast, and then guarantee follow-up diesel engine job stabilization and maintenance safety.

As shown in fig. 2, in order to make the spring 6 have different pre-tightening forces so as to make the outer valve core 2 abut against the valve seat 1, the pressure limiting valve preferably further comprises a pressure regulating gasket 5, and the pressure regulating gasket 5 is located between the spring 6 and the outer valve core 2. By replacing pressure regulating spacers 5 of different thicknesses, the spring 6 can have different precompression amounts, and thus the spring 6 can have different elastic forces.

In order to fix the pressure regulating gasket 5, a step hole is formed in the pressure regulating gasket 5, the upper end of the outer valve core 2 abuts against the step surface of the step hole, and the inner valve core 3 abuts against the shell 7 after penetrating through the step hole.

Preferably, the housing 7 is provided with a limit boss 72, and the upper end of the inner core 3 can abut against the limit boss 72.

In order to facilitate the installation of the pressure regulating gasket 5, the housing 7 is provided with an avoiding groove 71, and the pressure regulating gasket 5 is arranged in the avoiding groove 71. The upper end of the outer valve core 2 extends out of the inner accommodating cavity 22, and the upper end of the inner valve core 3 extends out of the inner accommodating cavity 22 and is accommodated in the avoiding groove 71.

Preferably, the relief groove 71 is a stepped groove, and the upper end of the valve seat 1 abuts against a stepped surface of the stepped groove to fix the valve seat 1. The pressure regulating gasket 5 is located on the upper side of the valve seat 1 and can reciprocate between the groove bottom of the avoiding groove 71 and the valve seat 1, so that the outer valve core 2 can reciprocate up and down.

In order to avoid the spring 6 from bending after being compressed, preferably, the housing 7 is provided with an annular guide groove 73, the spring 6 is arranged in the annular guide groove 73, the upper end of the spring 6 abuts against the bottom of the annular guide groove 73, and the lower end of the spring 6 abuts against the pressure regulating gasket 5.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A pressure limiting valve, comprising:

the valve seat (1) is provided with an oil drainage hole (11), and the valve seat (1) is abutted to the common rail system (100);

the outer valve core (2) is arranged on the valve seat (1) in a sliding mode, an inner containing cavity (22) and a pressure reducing oil hole (21) which are communicated with each other are formed in the outer valve core (2), and fuel oil of the common rail system (100) can flow into the inner containing cavity (22) from the pressure reducing oil hole (21);

the valve core comprises a shell (7) and a spring (6), wherein one end of the spring (6) is abutted against the shell (7), and the other end of the spring (6) is abutted against the outer valve core (2);

the inner valve core (3) is arranged in the inner accommodating cavity (22), one end of the inner valve core (3) can be spaced from the oil outlet end of the pressure reducing oil hole (21), and the other end of the inner valve core (3) can be abutted against the outer shell (7);

the outer valve core (2) can be in a sealing position for sealing the oil drain hole (11) and an opening position for opening the oil drain hole (11) under the combined action of the acting force of the spring (6), the fuel pressure in the inner accommodating cavity (22) and the fuel pressure of the common rail system (100).

2. The pressure limiting valve according to claim 1, wherein the outer spool (2) can abut against the inner wall of the oil release hole (11) and form a sealing line, and the cross-sectional area of the inner accommodating cavity (22) is larger than that of the relief oil hole (21) and smaller than the sealing area enclosed by the sealing line.

3. Pressure limiting valve according to claim 1, characterized in that the inner spool (3) is provided with a clearance from the inner wall of the inner receiving chamber (22).

4. The pressure limiting valve according to claim 3, wherein the valve seat (1) is further provided with an oil return hole (13), and the oil return hole (13) is used for discharging fuel flowing out from the oil drain hole (11) and the gap.

5. The pressure limiting valve according to claim 1, wherein an outer accommodating cavity (12) is further formed in the valve seat (1), the outer accommodating cavity (12) is communicated with the oil drainage hole (11) and is located at an oil outlet end of the oil drainage hole (11), and the outer valve core (2) is slidably arranged in the outer accommodating cavity (12).

6. The pressure limiting valve according to claim 5, characterized in that the pressure limiting valve further comprises a guide sleeve (4), the guide sleeve (4) is arranged in the outer accommodating cavity (12), and the outer valve core (2) is slidably arranged through the guide sleeve (4).

7. The pressure limiting valve according to claim 1, characterized in that it further comprises a pressure regulating gasket (5), said pressure regulating gasket (5) being located between said spring (6) and said outer spool (2).

8. The pressure limiting valve according to claim 7, wherein a stepped hole is formed in the pressure regulating gasket (5), the other end of the outer valve core (2) abuts against a stepped surface of the stepped hole, and the inner valve core (3) passes through the stepped hole and then abuts against the outer shell (7).

9. The pressure limiting valve according to claim 7, characterized in that the housing (7) is provided with an avoiding groove (71), and the pressure regulating gasket (5) is arranged in the avoiding groove (71).

10. Pressure limiting valve according to claim 1, characterized in that the housing (7) is provided with an annular guide groove (73), the spring (6) being arranged in the annular guide groove (73).