CN219605448U - Double-layer common rail pipe - Google Patents

Abstract

The scheme relates to a double-layer common rail pipe which is used for a medium-high speed diesel engine, the system pressure is more than or equal to 180MPa, and the double-layer common rail pipe has the functions of overpressure protection of the system, fault oil breaking of an oil sprayer, automatic pressure relief during shutdown and abnormal leakage oil collection. The assembly comprises: the inner layer pipe, multiple different types of brackets sleeved on the outer circle of the inner layer pipe, and an outer layer pipe assembled between adjacent brackets and sleeved on the outer circle of the inner layer pipe; a leakage oil flowing space is formed between the inner layer pipe and the outer layer pipe, and a leakage oil recovery oil duct communicated with the leakage oil flowing space is arranged on the first type support; the first type bracket is provided with a safety valve component, and part of the safety valve component penetrates through the first type bracket and then stretches into the inner layer pipe; the second type bracket is provided with a flow limiting valve component; a PCV valve mounting seat is assembled on a third type of bracket in the plurality of different types of brackets, and part of the PCV valve mounting seat penetrates through the third type of bracket and then stretches into the inner layer pipe; the two ends of the inner layer pipe are also provided with plugging components for plugging the two ends of the inner layer pipe.

Description

Double-layer common rail pipe

Technical Field

The utility model belongs to the technical field of high-pressure common rails of medium-high speed diesel engines, and particularly relates to a double-layer common rail pipe with system pressure not less than 180 MPa.

Background

With increasingly stringent emission regulations and increasingly stringent energy crisis, diesel fuel systems have increasingly employed high pressure common rail systems. The high-pressure common rail system has the characteristics of high injection pressure, high response speed, flexible control and the like, and can meet increasingly strict emission regulations and requirements of users on fuel economy and emission. One of the important means of improving fuel economy and emissions from diesel engines is to increase the pressure in the high pressure common rail system. Along with the continuous improvement of the pressure of the high-pressure common rail system, the traditional high-pressure common rail system is difficult to meet the requirements in the aspects of functionality, reliability, safety and the like.

Disclosure of Invention

The utility model aims to provide a double-layer common rail pipe which is used for a medium-high speed diesel engine, has the system pressure of more than or equal to 180MPa, and has the functions of overpressure protection of the system, fault oil breaking of an oil sprayer, automatic pressure relief when the engine is stopped and abnormal leakage oil collection.

The utility model is realized by the following technical scheme:

the utility model provides a double-layer common rail pipe, which comprises:

the inner layer tube, multiple different types of brackets sleeved on the outer circle of the inner layer tube, and the outer layer tube assembled between adjacent brackets and sleeved on the outer circle of the inner layer tube;

an oil seepage flow space is formed between the inner layer pipe and the outer layer pipe, and a leakage oil recovery oil duct communicated with the oil seepage flow space is arranged on a first type support in a plurality of different types of supports;

a safety valve assembly is assembled on a first type support in a plurality of different types of supports, and part of the safety valve assembly penetrates through the first type support and then stretches into the inner layer pipe;

a second type support in the plurality of different types of supports is provided with a flow limiting valve assembly, and a part of the flow limiting valve assembly penetrates through the second type support to form a seal with the inner layer pipe so as to block high-pressure oil in the inner layer pipe from supplying fuel to the fuel injector, or a part of the flow limiting valve assembly penetrates through the second type support to form a gap between the second type support and the inner layer pipe so as to supply the high-pressure oil in the inner layer pipe to the fuel injector;

a PCV valve mounting seat is assembled on a third type of bracket in the plurality of different types of brackets, and part of the PCV valve mounting seat penetrates through the third type of bracket and then stretches into the inner layer pipe;

and the two ends of the inner layer pipe are also provided with plugging components for plugging the two ends of the inner layer pipe.

Preferably, conical surfaces are formed at two ends of an inner hole of the inner layer pipe respectively, and external threads are arranged on outer walls of two ends of the inner layer pipe;

the plugging assembly comprises a plug and a cap;

the plugs are respectively blocked at two ends of the inner hole of the inner layer pipe, and each plug is provided with a spherical surface which is closely contacted with the conical surface of the end part of the inner hole of the inner layer pipe;

the two ends of the inner layer pipe are respectively sleeved with a cap, and the caps are fastened on the external threads of the inner layer pipe and compress the plugs, so that the spherical surfaces of the plugs are in close contact with the conical surfaces of the end parts of the inner holes of the inner layer pipe.

Preferably, an annular groove is formed in the outer wall of the outer layer tube, and an O-shaped sealing ring tightly attached to the inner wall of the first type support is installed in the annular groove.

Preferably, the second type bracket is provided with an inner hole sleeved on the outer layer pipe, the inner hole is in a step hole design, the step hole comprises a middle hole positioned in the middle and end holes positioned at two sides of the middle hole, and the aperture of the middle hole is smaller than that of the end holes;

the second type of support is sleeved on the outer layer tube by means of the end holes and sleeved on the inner layer tube by means of the middle holes.

Preferably, the outer wall of the inner layer pipe is provided with a first channel for leading high-pressure oil supplied by the inner layer pipe into the oil sprayer by the flow limiting valve assembly, one side of the first channel communicated with the outer wall of the inner layer pipe is a conical channel, and one side of the first channel communicated with the inner wall of the inner layer pipe is a circular channel;

wherein, the conical surface of the conical channel of the first channel is used for forming conical surface seal with the flow limiting valve component;

and the outer wall of the inner layer pipe is also provided with a positioning hole which is not communicated with the inner wall of the inner layer pipe.

Preferably, the PCV valve is mounted to a third type of bracket through the PCV valve mount;

the outer wall of the inner layer pipe is also provided with a second channel for realizing the pressure relief of the PCV valve in the inner layer pipe, one side of the second channel communicated with the outer wall of the inner layer pipe is a conical channel, and the side of the second channel communicated with the inner wall of the inner layer pipe is a circular channel;

the ball head of the PCV valve mounting seat penetrates through the third type bracket to form conical surface fit with the conical channel of the second channel, and a pressure relief channel communicated with the circular channel of the second channel is formed in the ball head of the PCV valve mounting seat;

the ball head of the PCV valve mount is assembled to the third type of bracket by an inner tightening cap and an outer tightening cap.

Preferably, a third channel for the safety valve assembly to decompress the fuel in the inner layer pipe is arranged on the outer wall of the inner layer pipe, one side of the third channel communicated with the outer wall of the inner layer pipe is a conical channel, and one side of the third channel communicated with the inner wall of the inner layer pipe is a circular channel;

the relief valve assembly includes: the safety valve comprises a safety valve body, a safety valve core, a safety valve spring, a sliding block, a safety valve connector and a pressure regulating screw rod;

the safety valve core is assembled in a groove on one side of the safety valve body, which faces the safety valve joint;

the safety valve spring is assembled in a groove on one side of the safety valve core, which faces the safety valve connector, and a groove on one side of the safety valve connector, which faces the safety valve core;

and the slider is assembled in the safety valve joint and is contacted with the safety valve spring;

one end of the pressure regulating screw is inserted into the safety valve connector to be in contact with the sliding block, and the part of the pressure regulating screw outside the safety valve connector is locked by a hexagonal nut, so that the pretightening force of the safety valve spring is set;

one end of the safety valve body penetrates through the first type support to form conical surface seal with the conical channel of the third channel, and the safety valve body is provided with a flow channel communicated with the circular channel of the third channel.

Preferably, the safety valve body is securely connected to the first type of bracket by an outer tightening cap and an inner tightening cap.

Preferably, the flow restricting valve assembly comprises: the device comprises a flow limiting valve seat, a flow limiting valve shell, a flow limiting valve and a flow limiting valve spring;

the flow limiting valve shell is arranged above the flow limiting valve seat, a groove is formed in the flow limiting valve shell facing the flow limiting valve seat, and a flow passage communicated with the groove is formed in one side of the flow limiting valve shell, which is away from the flow limiting valve seat;

the restrictor valve fits into the groove of the restrictor valve housing;

the flow limiting valve spring is arranged between the flow limiting valve and the bottom of the groove of the flow limiting valve shell;

a flow passage is arranged on one side of the flow limiting valve facing the flow limiting valve seat, and an inclined through hole which can communicate the flow passage with the flow passage is also arranged on the flow limiting valve;

the flow-limiting valve seat is provided with a flow passage communicated with the flow passage;

the flow restricting valve seat forms a cone seal through the cone of the cone passage of the first passage.

The utility model adopts the technical proposal and has the following advantages:

1. the whole inner layer pipe assembly adopts a double-layer design, the inner layer pipe bears high pressure in the pipe, and the outer layer pipe collects abnormal oil leakage at each sealing surface and is led out through a pipeline. In such design, no matter the inner layer pipe is cracked due to special conditions or each high-pressure sealing cover fails, high-pressure oil can not be directly sprayed to the external environment, but enters the inner layer pipe, and safety accidents are avoided.

2. The safety valve component is integrated on the inner layer pipe, so that an overpressure protection effect can be achieved, when the pressure in the inner layer pipe exceeds a set value, the valve core of the safety valve moves upwards under the action of hydraulic pressure and overcomes the spring force of the safety valve spring, hydraulic oil flows away through a gap between the valve core of the safety valve and a valve seat of the safety valve, and the inner layer pipe burst caused by infinite rising of the pressure in the pipe is prevented.

3. The inner layer pipe is integrated with a flow limiting valve component, when the high-pressure oil pipe leaks or the oil sprayer leaks and sprays abnormally, the fuel supply of the oil sprayer is cut off, and the problems of fire explosion, personnel safety and the like are prevented.

4. And a normally open electromagnetic valve is integrated on the inner layer pipe and used for reducing the pressure in the inner layer pipe after the test is finished, so that other personnel can be prevented from dismantling the common rail pipe under pressure, and personal injury is caused.

5. The matched use of the inner tightening cap and the outer tightening cap enables the installation direction of the PCV valve installation seat to be freely adjusted, which is particularly important for diesel engines with extremely compact structures.

6. The screw hole below the second type support is used for installing a set screw, and the relative position between the second type support and the inner layer pipe is determined through the cooperation of the set screw and the positioning hole of the inner layer pipe. Therefore, after other parts are screwed into the second type bracket through the threaded holes of the second type bracket, the center line of the ball head and the center line of the conical surface of the inner tube are overlapped together, so that a good sealing effect is realized.

7. One end of a flow-limiting valve seat of the flow-limiting valve assembly adopts a ball head design and forms ball head-cone seal with the cone surface of the inner layer pipe; one end adopts concentric double-ring groove plane design, and forms plane-plane seal with the lower end face of the flow-limiting valve shell, so that the ball head below can automatically align the center of the conical surface of the inner tube, and the sealing effect is further improved.

8. The maximum distance of the lifting of the safety valve core of the safety valve assembly is limited by the safety valve connector, so that the spring is prevented from being broken due to the fact that the lifting distance is too large and exceeds the pressure and height of the spring.

Drawings

Fig. 1 is an overall construction diagram of a double-layer common rail pipe of the present embodiment;

FIG. 2 is an enlarged view of a portion of FIG. 1 at A;

FIG. 3 is an enlarged view of a portion of FIG. 1 at B;

fig. 4 is a structural view of the safety valve assembly of the present embodiment;

FIG. 5 is a block diagram of the restrictor valve assembly of the present embodiment;

FIG. 6 is a structural view of the flow restricting valve seat of the present embodiment;

fig. 7 is a structural view of the bracket of the present embodiment.

Detailed Description

The utility model is described in more detail below with reference to the accompanying drawings:

as shown in fig. 1 to 7, the present embodiment provides a double-layer common rail pipe including an inner layer pipe 3, a safety valve assembly 20, a flow limiting valve assembly 7, a first type bracket 9, a second type bracket 1, a third type bracket 10, a plug 5, a cap 4, an outer layer pipe, an inner tightening cap 14, an outer tightening cap 13, a PCV valve mount 15, a PCV valve 16, a rail pressure sensor 17, and the like, the common rail pipe assembly integrally adopts a double-layer design, the inner layer pipe 3 of the inner layer bears high pressure in the pipe, and the outer layer pipe 8 collects abnormal oil leakage at each sealing surface and then is led out through a pipeline.

The safety valve assembly 20 plays a role in overpressure protection, and when the pressure in the inner pipe 3 exceeds a set value, the valve is opened to release pressure, so that the common rail pipe burst caused by infinite rising of the pressure in the pipe is prevented.

The flow limiting valve assembly 7 is positioned between the common rail pipe and the fuel injector, and cuts off the high-pressure oil supply of the inner layer pipe 3 to the fuel injector when the high-pressure oil pipe leaks or the fuel injector leaks and is abnormally sprayed, so that the problems of fire explosion, personnel safety and the like are prevented.

The PCV valve 16 is a normally open solenoid valve for reducing the pressure in the common rail after the test is completed.

As shown in fig. 1 and 2, the inner tube 3 is designed as a through hole in the horizontal direction, and two ends of the inner tube are provided with conical surfaces and threads. The cap 4 is fastened to the screw and presses the spherical surface of the cap 5, and the spherical surface of the cap 5 is in close contact with the tapered surface of the inner tube 3, thereby achieving sealing.

As shown in fig. 2, a channel 31 for guiding high-pressure oil supplied by the inner tube 3 into the fuel injector by the flow limiting valve assembly 7 is arranged on the outer wall of the inner tube 3 in the vertical direction (i.e. in the radial direction of the inner tube 3), one side of the channel 31 communicated with the outer wall of the inner tube 3 is a conical channel, and one side of the channel 31 communicated with the inner wall of the inner tube 3 is a circular channel, wherein the conical surface of the conical channel is used for forming conical surface sealing or clearance with the flow limiting valve assembly 7.

As shown in fig. 2, a positioning hole 32 is further provided on the outer wall of the inner tube 3, and the positioning hole 32 is not connected to the inner wall of the inner tube 3.

As shown in fig. 2, the outer tube 8 is designed in concentric circles, and an annular groove 81 is formed on the outer wall of the outer tube for installing the O-ring 6, and the O-ring 6 is tightly matched with the inner wall of the first type bracket 9.

As shown in fig. 2, the inner hole of the second type bracket 1 is designed by adopting a stepped hole (for the stepped hole, the stepped hole is seen from the length direction of the common rail pipe and comprises two end holes with larger apertures at two sides and a middle hole with smaller middle aperture, the middle hole is arranged between the two end holes), and the outer diameters of the middle hole and the inner layer pipe 3 are the same, so that a large contact area exists between the middle hole and the inner layer pipe, and good support left and right are achieved; the end holes at the two ends are used for being matched with the outer layer tube 8 to form a sealed space.

As shown in fig. 2, the threaded hole below the second type bracket 1 is used for installing a set screw 2, and the relative position between the second type bracket 1 and the inner tube 3 is determined by the cooperation of the set screw 2 and the positioning hole 32 of the inner tube 3.

As shown in fig. 3, the outer wall of the inner layer pipe 3 is further provided with a second channel for implementing the pressure relief of the PCV valve 15 in the inner layer pipe 3, wherein one side of the second channel communicated with the outer wall of the inner layer pipe 3 is a conical channel, and one side of the second channel communicated with the inner wall of the inner layer pipe 3 is a circular channel; after passing through the third type bracket 10 and the outer tube 8, the bulb of the PCV valve installation seat 15 forms conical surface fit with the conical channel of the second channel, and a pressure relief channel which is communicated with the circular channel of the second channel is formed inside the bulb of the PCV valve installation seat 15, so that the pressure relief channel is communicated with the outside or blocked from being communicated with the outside through the manipulation of the PCV valve 16, and the pressure in the inner tube 3 is relieved or not relieved.

As shown in fig. 3, the ball of the PCV valve installation seat 15 is assembled to the third type bracket 10 through the inner tightening cap 14 and the outer tightening cap 13, the outer tightening cap 13 is fastened to the third type bracket 10 through threads, the inner tapered surface thereof compresses the inner tightening cap 14, and the inner tightening cap 14 is fastened together through left-handed threads and the ball of the PCV valve installation seat 15, thereby compressing the ball of the PCV valve installation seat 15 and the tapered surface of the inner tube 3, and sealing is achieved.

An O-ring 18 is fitted between the ball head of the PCV valve mount 15 and the inner tightening cap 14, and an O-ring 19 is fitted between the inner tightening cap 14 and the outer tightening cap 13.

In this embodiment, a third channel for the relief valve assembly 20 to relieve pressure of the fuel in the inner tube 3 is provided on the outer wall of the inner tube 3, one side of the third channel, which is communicated with the outer wall of the inner tube 3, is a conical channel, and one side of the third channel 31, which is communicated with the inner wall of the inner tube 3, is a circular channel.

As shown in fig. 4, the relief valve assembly 20 in the present embodiment includes a pressure adjusting screw 21, a relief valve joint 23, a slider 24, a relief valve spring 27, a relief valve spool 28, a relief valve body 29, and the like. The relief valve spool 28 is fitted in a groove of the relief valve body 29 on the side facing the relief valve joint 23; the relief valve spring 27 is fitted in a groove on a side of the relief valve spool 28 facing the relief valve joint 23 and a groove on a side of the relief valve joint 23 facing the relief valve spool 28; and the slider 24 is fitted in the relief valve joint 23 and contacts the relief valve spring 27; one end of the pressure regulating screw 21 is inserted into the safety valve connector 23 to be in contact with the sliding block 24, and the part of the pressure regulating screw 21 outside the safety valve connector 23 is locked by the hexagonal nut 22, so that the pretightening force of the safety valve spring 27 is set. Referring to fig. 4, the lower end of the relief valve body 29 forms a conical surface seal with the conical passage of the third passage after passing through the first type bracket 9 and the outer tube, and the relief valve body 29 is provided with a flow passage 291 communicating with the circular passage of the third passage. The opening pressure of the relief valve assembly 20 is set by rotating the pressure regulating screw 21 to change the preload of the relief valve spring 27.

The pressure regulating screw 21 is locked by the type 1 hexagonal nut 22, so that the pressure regulating screw is prevented from being separated due to vibration in the running process.

As shown in fig. 4, the lower end of the safety valve body 29 adopts a left-hand thread 292, a conical surface is arranged at the end of the left-hand thread 292, the left-hand thread 292 is used for being matched with an inner tight cap, and the inner tight cap is tightly connected with the first type bracket 9 by means of an outer tight cap. The middle part of the safety valve body 29 is provided with a middle hole and a conical surface which are matched with the safety valve core 19; the upper part of the safety valve body 29 is provided with a threaded hole matched with the safety valve joint 23, and the two parts are sealed by adopting a plane; the side is provided with a threaded hole for oil discharge. The manner of assembling the relief valve body 29 and the first-type bracket 9 in the present embodiment is identical to the manner of assembling the PCV valve mount 15 and the third-type bracket 10, and the manner of assembling the relief valve body 29 on the first-type bracket 9 can be understood with reference to the manner of assembling the ball head of the PCV valve mount 15 on the third-type bracket 10 in fig. 3.

The safety valve core 28 has two stages of conical surfaces at the end, a through hole in the middle and a spring mounting hole in the upper.

An O-ring 25 is provided between the relief valve joint 23 and the slider 24, and an O-ring 26 is provided between the relief valve joint 23 and the relief valve body 29.

When the pressure in the inner pipe 3 does not exceed the opening pressure of the safety valve assembly 20, the safety valve core 28 is tightly pressed on the conical surface of the safety valve body 29 under the action of the safety valve spring 27, and the hydraulic oil in the inner pipe 3 cannot flow out through the flow passage 291; when the pressure in the inner pipe 3 exceeds the opening pressure of the relief valve assembly 20, the relief valve spool 28 will move upward against the spring force of the relief valve spring 27 under the action of hydraulic pressure, and hydraulic oil will flow away through the flow passage 291 and the gap between the relief valve spool 28 and the relief valve body 29, preventing the inner pipe 3 from bursting due to an infinite rise in pressure in the common rail. The maximum distance that the relief valve spool 28 rises is limited by the relief valve joint 23, preventing the relief valve spring 27 from breaking due to the excessive rising distance reaching the pressure and height of the relief valve spring 27. The opening pressure of the relief valve assembly 20 is set by rotating the pressure regulating screw 21 to change the preload of the relief valve spring 27.

As shown in fig. 5 and 6, the restrictor valve assembly 7 in the present embodiment includes a restrictor valve spring 75, a restrictor valve housing 72, a restrictor valve 73, an O-ring 74, and a restrictor valve seat 71.

As shown in fig. 5, restrictor valve housing 72 is disposed above restrictor valve seat 71, restrictor valve housing 72 is formed with a groove facing restrictor valve seat 71, and a side of restrictor valve housing 72 facing away from restrictor valve seat 71 is provided with a flow passage 721 communicating with the groove;

restrictor valve 73 fits into a groove of restrictor valve housing 72;

a restrictor valve spring 75 is disposed between restrictor valve 73 and the bottom of the groove of restrictor valve housing 72;

the flow-limiting valve 73 is provided with a flow passage 732 on one side facing the flow-limiting valve seat 71, and the flow-limiting valve 73 is also provided with an inclined through-flow hole 731 for communicating the flow passage 732 with the flow passage 721;

the restrictor valve seat 71 has a flow passage 711 communicating with the flow passage 732;

the restrictor seat 71 forms a cone seal through the cone of the cone-shaped passage of the first passage 31.

An O-ring 74 fitted around the outer circumference of the restrictor valve housing 72 is used to form a seal with the second type of carrier 1.

As shown in fig. 5, the middle part of the flow limiting valve 73 is provided with an inclined through hole 731, and the top part is provided with a double conical surface. When the high-pressure oil pipe leaks or the oil injector leaks and abnormal injection occurs, the limiting valve 73 moves upwards against the spring force of the limiting valve spring 75 under the action of the internal and external pressure difference, the top conical surface contacts with the inner conical surface of the limiting valve housing 72, and the fuel supply of the oil injector by the inner layer pipe 3 is cut off. When the high-pressure oil pipe is not leaked and the injector is not leaked and is not abnormally injected, the fuel supplied from the inner pipe 3 flows into the injector through the flow passage 711 of the restrictor valve seat 71, the inner flow passage 732 of the restrictor valve 73, the diagonal flow passage 731 of the restrictor valve housing 72, and the inner flow passage 721.

One end of the flow-limiting valve seat 71 adopts a ball head design and forms ball head-cone seal with the cone surface of the inner tube 3; one end is designed in a concentric double ring groove flat surface to form a flat-to-flat seal with the lower end face of the restrictor valve housing 72.

Each high pressure seal includes a gap between the plug 5 and the inner tube 3, a gap between the restrictor valve seat 71 and the inner tube 3, and a gap between the restrictor valve seat 71 and the restrictor valve housing 72, and abnormal leakage oil between the safety valve assembly 20 and the inner tube 3 flows between the inner tube 3 and the outer tube 8, and is then led out through the leakage oil recovery oil passage 11 of m12x1.5 on the first type bracket 9.

When the double-layer common rail pipe is assembled, the second type support 1 is assembled from left to right, the middle hole of the second type support 1 penetrates through the outer diameter of the inner layer pipe 3, the set screw 2 and the outer layer pipe 8 are assembled, and the subsequent support and the outer layer pipe 8 are assembled in sequence. Two end caps 5 are then installed, the cap 4 is then screwed on, and the restrictor valve assembly 7 is then installed. The outer tightening cap 14 is first sleeved into the PCV valve mount 15, then the inner tightening cap 13 is screwed onto the PCV valve mount 15, the direction of the PCV valve mount 15 is adjusted, and finally the outer tightening cap 14 is screwed onto the third type of bracket 10.

Claims (9)

1. A double-layer common rail pipe, comprising:

an inner layer tube (3), a plurality of different types of brackets sleeved on the outer circle of the inner layer tube (3) and an outer layer tube (8) assembled between adjacent brackets and sleeved on the outer circle of the inner layer tube (3);

an oil leakage flow space is formed between the inner layer pipe (3) and the outer layer pipe (8), and a leakage oil recovery oil duct (11) communicated with the oil leakage flow space is arranged on a first type bracket (9) in a plurality of different types of brackets;

a safety valve assembly (20) is assembled on a first type support (9) in a plurality of different types of supports, and part of the safety valve assembly (20) penetrates through the first type support (9) and then extends into the inner layer pipe (3);

a second type bracket (1) in a plurality of different types of brackets is provided with a flow limiting valve assembly (7), a part of the flow limiting valve assembly (7) passes through the second type bracket (1) and forms a seal with the inner layer pipe (3) to block high-pressure oil in the inner layer pipe (3) from supplying fuel to the fuel injector, or a gap for supplying the high-pressure oil in the inner layer pipe (3) to the fuel injector is formed between the part of the flow limiting valve assembly (7) and the inner layer pipe (3) after passing through the second type bracket (1);

a third type of support (10) of a plurality of different types of supports is provided with a PCV valve installation seat (15), and part of the PCV valve installation seat (15) penetrates through the third type of support (10) and then stretches into the inner layer pipe (3);

the two ends of the inner layer pipe (3) are also provided with plugging components for plugging the two ends of the inner layer pipe.

2. The double-layer common rail pipe according to claim 1, wherein conical surfaces are formed at two ends of an inner hole of the inner pipe (3), and external threads are arranged on outer walls of two ends of the inner pipe (3);

the plugging assembly comprises a plug (5) and a cap (4);

the plugs (5) are respectively plugged at two ends of an inner hole of the inner layer pipe (3), and the plugs (5) are provided with spherical surfaces with conical surfaces closely contacted with the end parts of the inner hole of the inner layer pipe (3);

the two ends of the inner layer pipe (3) are respectively sleeved with a cap (4), and the caps (4) are fastened on the external threads of the inner layer pipe (3) and compress the plug (5) so that the spherical surface of the plug (5) is tightly contacted with the conical surface of the end part of the inner hole of the inner layer pipe (3).

3. The double-layer common rail pipe according to claim 1, wherein an annular groove (81) is formed in the outer wall of the outer layer pipe (8), and an O-shaped sealing ring (6) tightly attached to the inner wall of the first type bracket (9) is installed in the annular groove (81).

4. The double-layer common rail pipe according to claim 1, characterized in that the second type bracket (1) is provided with an inner hole sleeved on the outer layer pipe (8), the inner hole is of a step hole design, the step hole comprises a middle hole positioned in the middle and end holes positioned at two sides of the middle hole, and the aperture of the middle hole is smaller than that of the end holes;

the second type bracket (1) is sleeved on the outer layer pipe (8) by virtue of the end hole and is sleeved on the inner layer pipe (3) by virtue of the middle hole.

5. The double-layer common rail pipe according to claim 1, wherein the outer wall of the inner layer pipe (3) is provided with a first channel (31) for leading high-pressure oil supplied by the inner layer pipe (3) into the oil injector by the flow limiting valve assembly (7), one side of the first channel (31) communicated with the outer wall of the inner layer pipe (3) is a conical channel, and one side of the first channel (31) communicated with the inner wall of the inner layer pipe (3) is a circular channel;

wherein the conical surface of the conical channel of the first channel (31) is used for forming conical surface sealing with the flow limiting valve assembly (7);

the outer wall of the inner layer pipe (3) is also provided with a positioning hole (32), and the positioning hole (32) is not communicated to the inner wall of the inner layer pipe (3).

6. The double-layer common rail pipe according to claim 1, characterized in that a PCV valve (16) is mounted to a third type of bracket (10) through the PCV valve mount (15);

the outer wall of the inner layer pipe (3) is also provided with a second channel for realizing pressure relief of the PCV valve (16) in the inner layer pipe (3), one side of the second channel communicated with the outer wall of the inner layer pipe (3) is a conical channel, and one side of the second channel communicated with the inner wall of the inner layer pipe (3) is a circular channel;

the ball head of the PCV valve mounting seat (15) passes through the third type bracket (10) and forms conical surface fit with the conical channel of the second channel, and a pressure relief channel communicated with the circular channel of the second channel is formed in the ball head of the PCV valve mounting seat (15);

a bulb of the PCV valve mounting seat (15) is assembled to the third type bracket (10) through an inner tightening cap (14) and an outer tightening cap (13).

7. The double-layer common rail pipe according to claim 1, wherein a third channel for the safety valve assembly (20) to release the fuel in the inner layer pipe (3) is arranged on the outer wall of the inner layer pipe (3), one side of the third channel communicated with the outer wall of the inner layer pipe (3) is a conical channel, and one side of the third channel communicated with the inner wall of the inner layer pipe (3) is a circular channel;

the relief valve assembly (20) includes: a safety valve body (29), a safety valve spool (28), a safety valve spring (27), a sliding block (24), a safety valve joint (23) and a pressure regulating screw (21);

the safety valve core (28) is assembled in a groove on one side of the safety valve body (29) facing the safety valve joint (23);

the safety valve spring (27) is assembled in a groove on one side of the safety valve spool (28) facing the safety valve joint (23) and a groove on one side of the safety valve joint (23) facing the safety valve spool (28);

and the slider (24) is fitted in the relief valve joint (23) and is in contact with the relief valve spring (27);

one end of the pressure regulating screw rod (21) is inserted into the safety valve connector (23) to be in contact with the sliding block (24), and the part of the pressure regulating screw rod (21) outside the safety valve connector (23) is locked by the hexagonal nut (22) so as to set the pretightening force of the safety valve spring (27);

one end of the safety valve body (29) penetrates through the first type support (9) to form conical surface sealing with the conical channel of the third channel, and the safety valve body (29) is provided with a first flow channel (291) communicated with the circular channel of the third channel.

8. Double-layer common rail pipe according to claim 7, characterized in that the safety valve body (29) is fastened to the first type bracket (9) by means of an outer and an inner tightening cap.

9. The double-layer common rail pipe according to claim 5, characterized in that the restrictor valve assembly (7) comprises: a restrictor valve seat (71), a restrictor valve housing (72), a restrictor valve (73) and a restrictor valve spring (75);

the flow limiting valve housing (72) is arranged above the flow limiting valve seat (71), a groove is formed in the flow limiting valve housing (72) towards the flow limiting valve seat (71), and a second flow passage (721) communicated with the groove is formed in one side of the flow limiting valve housing (72) away from the flow limiting valve seat (71);

a restrictor valve (73) fits into a groove of the restrictor valve housing (72);

the limiting valve spring (75) is arranged between the limiting valve (73) and the groove bottom of the groove of the limiting valve shell (72);

a third flow passage (732) is arranged on one side of the flow limiting valve (73) facing the flow limiting valve seat (71), and an inclined through hole (731) which can communicate the third flow passage (732) with the second flow passage (721) is also arranged on the flow limiting valve (73);

the flow-limiting valve seat (71) is provided with a fourth flow passage (711) communicated with the third flow passage (732);

the restrictor seat (71) forms a cone seal through the cone of the cone passage of the first passage (31).