WO2018134144A1

WO2018134144A1 - High-pressure accumulator of a high-pressure fuel injection system

Info

Publication number: WO2018134144A1
Application number: PCT/EP2018/050822
Authority: WO
Inventors: Philippe Allio
Original assignee: Robert Bosch Gmbh
Priority date: 2017-01-19
Filing date: 2018-01-15
Publication date: 2018-07-26
Also published as: KR20190103390A; EP3571387B1; CN110234865A; JP2020505548A; FR3061934A1; JP6855582B2; CN110234865B; EP3571387A1; FR3061934B1

Abstract

The invention relates to a high-pressure accumulator for a high-pressure injection system made of a cylindrical body (11), which delimits a high-pressure chamber (12, 12a), and connection pieces (13, 13a), which are provided with outlet passages (131, 131a) for a high-pressure liquid, said passages opening into the chamber (12, 12a), and each of which is provided with a throttle in order to weaken pressure waves generated by injectors connected downstream. Each of the connection pieces (13, 13a) has a passage (131, 131a) with a chamber (1312, 1312a) at the outlet, said chamber receiving an insert piece (2, 2a) which is provided with the throttle (22, 22a). The insert piece (2, 2a) is fixed in the chamber (1312, 1312a) in a force-fitting manner by an autofrettage process of the high-pressure accumulator.

Description

High-pressure accumulator of a high-pressure fuel injection system Field of the invention

The present invention relates to a high pressure accumulator for a high pressure injection system formed of a cylindrical body defining a high pressure chamber and fittings connected to high pressure liquid discharge passages opening into the chamber and having a throttle around the pressure waves attenuate that are generated by downstream injectors.

State of the art

Such a high-pressure accumulator of a high-pressure injection system, which is shown in FIG. 7, is already known. This rail 100, also called "high-pressure accumulator", is formed by a cylindrical body 111 of thick forged steel surrounding a high-pressure chamber 112. The body of the rail has outlet fittings 113 for connecting the high-pressure lines, which are each connected to an injector. These fittings 113 are traversed by a bore 114 which opens into the chamber 112. At the bottom of the bore at the junction with the chamber is a drilled restrictor 115. This restrictor 115 dampens the pressure waves caused by the closing movements of the injector The restrictor 115 created by the bore is sometimes called a "nozzle".

Although this solution makes it possible to dampen the pressure waves, but it has a number of disadvantages, in particular its effectiveness is relatively low, since the bore forming this throttle does not allow to create elaborate geometric shapes.

It is also not possible to comply with strict tolerances; In addition, the bore-shape design, at the level of the mouth of the passage into the chamber, creates an edge which produces strong dispersions in the damping of the waves. In order to avoid this, electrochemical processing of the edge of the mouth of the bore is necessary to round it off and eliminate any burrs, or any part that protrudes into the chamber, which is a difficult and therefore expensive process. In the prior art, there are also alternatives to the nozzles drilled in the rail in the form of plugged nozzles. These nozzles are plugged in a conventional manner, that is by the mastering of the negative geometric game (positive clamping) and the use of a press fit, the insertion forces are controlled. These plugged-in nozzles are only used for rails without autofrettage or with a low autofrettage, as the autofrettage causes residual deformations which make the mastering of the positive clamping too critical. In this case, an expensive additional reworking operation of the plug-in diameter would be required after autofrettage. This known solution thus has numerous disadvantages.

Object of the invention

The object of the present invention is to develop a high-pressure accumulator for a high-pressure injection system which makes it possible to effectively dampen the pressure waves generated in the rail by closing the injectors of the downstream injectors, which is at the same time easy to create and weak Dispersion of damping between nozzles of the same rail or generated by different rails.

Presentation and advantages of the invention

To this end, the present invention relates to a high-pressure accumulator for a high-pressure injection system for an internal combustion engine, which is formed from a cylindrical body which defines a high pressure chamber, and fittings. One or more connecting pieces are provided with one or more outlet passages for a high-pressure liquid, which open into the chamber. In the exit passage, a throttle is arranged to attenuate the pressure waves of a downstream injector. The fittings each have at the output a passage with a chamber which receives an insert, which is provided with the throttle. The insert is frictionally arranged in the chamber by an autofrettage process of the high-pressure accumulator.

The high pressure accumulator according to the invention is easy to manufacture and yet has a throttle with low tolerances. The fixed connection of the insert in the high-pressure accumulator takes place in a simple manner and without that new or other means are required, since this firm connection is made by the autofrettage of the rail. The Autofrettage of the rail is a well-known manufacturing process to ensure the fatigue behavior of the Rails. This does not extend the production cycle.

The choke, created outside of the rail, allows for easy manufacture by drilling and finishing operations outside the rail, without the risk of foreign bodies being introduced into the rail and avoiding any problem of burrs; on the contrary, this makes it possible to produce smooth edges or curves.

Thus, the passage of the inserts on a rounding at the junction on the side of the high-pressure chamber.

According to another advantageous feature is the

Passage in the insert a stepped bore, which is formed from a series of holes of decreasing diameter, which are separated by conical functions. Thus, there is a stepped throttle which allows the inserts to be better optimized for the compromise damping / loss of system effectiveness.

The series of decreasing diameter holes is just one example of complex geometry made possible by a nozzle being machined separately from the rail. The aim is to obtain an asymmetry of the pressure loss, that is less pressure loss in the direction that is useful for the injection, and more pressure loss in the direction that only contributes to the damping.

According to another feature, the passage with the throttle has a conical entrance, which forms a sealing seat for the Autofrettagevorgang.

According to another feature, the connector has a conical entrance, also here to make the tightness for the autofrettage.

According to a more specific feature, the chamber is cylindrical and forms with the bore a shoulder that creates a sealing edge. The insert has an outer surface with a large diameter cylindrical portion for clearance into the cylindrical chamber during assembly. Furthermore, the insert has a small diameter part which projects freely in the bore of the fitting, the two parts of the insert being connected by a conical segment intended to come against the edge of the fitting. In another feature, the fitting has a conical chamber which continues through a bore having a cross-section smaller than that of the small base of the conical chamber. And the insert with throttle has a conical body with a length which is smaller than the length of the conical chamber, and the cross section of its small base is larger than the cross section of the small base of the chamber, wherein the taper of the chamber and that of the conical Body are identical.

Advantageously, in the case of the conical chamber, the surface of the conical chamber and / or that of the conical body has inequalities, bumps and raised or recessed geometrical shapes for increasing the adhesion of the two surfaces in contact by autofrettage and also for better tightness in autofrettage ,

In another feature, the cross-section of the portion of the insert entering the bore is smaller than the cross-section of that bore so as not to be in contact with it after autofrettage of the rail and inserts.

In this way, the interface between the insert and the fitting is reduced by the single contact surface which can be tensioned by autofrettage.

According to another feature, the length of the part of the insert is smaller than the length of the bore, such that the mouth of the throttle is significantly removed from the mouth of the bore in the chamber. Thus, the exit of the bore of the insert will be well above the mouth of the bore in the chamber and will affect the pressure loss.

If the high-pressure accumulator has a plurality of connecting pieces, an insert piece with a throttle according to one of the embodiments described above is preferably arranged in each connecting piece, which leads to a downstream injector.

The object of the invention is also the production of a high pressure accumulator as defined above, this method being characterized in that

by milling a chamber is created in the exit passage of each fitting,

an insert is created which is traversed by a throttle, the outer diameter of the insert being adapted to that of the chamber, an insert is installed in each chamber,

the tightness of the inserts and those of the entry of the fittings is created and

the rail assembled in this manner is subjected to an autofrettage pressure to treat the inner surface of the rail and force fit the inserts in the chamber of the fittings.

As already stated above, the manufacturing process of the rail is particularly simple and at the same time offers the advantage of being able to create precise and effective throttles for damping the pressure waves (pressure surges).

drawings

The present invention will be described in more detail below by means of exemplary embodiments which are illustrated in the attached drawings, in which:

1 is an axial sectional view of a portion of a high-pressure accumulator of a

High-pressure injection system,

FIG. 2 is an axial sectional view of a throttle insert for the high pressure accumulator of FIG. 1;

FIG. 3 is a schematic half-sectional view of the embodiment of the high-pressure accumulator of FIG. 1,

Figure 4 is an axial sectional view of another embodiment of a high-pressure accumulator of an injection system according to the invention,

FIG. 5 is an axial section of the throttle insert for the high pressure accumulator of FIG. 4;

Figure 6 is a half-sectional view explaining the mounting of the throttle insert in a fitting of the high pressure accumulator of Figure 4; Figure 7 is a cross-sectional view of a known high pressure accumulator.

Description of the embodiments of the invention

According to FIG. 1, the invention relates to a rail or a high-pressure accumulator 1 of a high-pressure injection system in an internal combustion engine. A common part of this rail is shown in axial section. The other components of the injection system are not shown. The high-pressure accumulator 1 is a thick-walled forged steel cylindrical body 11 surrounding a high-pressure chamber 12 supplied with high-pressure fuel by the high-pressure pump for distributing the high-pressure fuel to the injectors controlled by the central control unit of the engine become.

The movement of the closing and that of the opening of the injectors create compression and depression waves C.Druckschläge "), which are transferred from the high-pressure liquid in the line connecting the injector to the rail 1, and thus enter the rail.

The cylindrical body 11 has connection pieces 13 for connection, which are respectively connected through a passage 131 to the high-pressure chamber 12 and through a high-pressure line to its injector. Externally, the fitting has a thread 132 to screw the connection of the high pressure line.

The example of Figure 1 is limited to the conventional part of the rail with two fittings 13, one is empty and the other has an insert 2 with throttle, represent. The rail 1 has as many fittings 13 and high-pressure fuel outlets, as it has supplied injectors. All of these fittings 13 preferably have the same structure, and the following description will be limited to one of them.

The connector 13 on the right side of Figure 1 shows its passage 131 without its insert with throttle 2; the fitting 13 on the left side is equipped with the insert with throttle 2.

The insert with throttle 2 is shown separately in section in Figure 2.

Referring to FIG. 1, the passage 131 in a fitting 13 after being aligned with the high pressure chamber 12 is formed from an inlet cone 1311 followed by a cylindrical chamber / bore 1312 having a diameter larger than that of the downstream bore 1314 is to form a sealing edge 1313. The passage 131 receives the insert with throttle 2.

2, the insert with throttle 2 has a cylindrical body 21 which is traversed by a stepped bore 22, which is formed from a series of holes with decreasing diameters 222, 224, 226, which are separated by conical connections 223, 225 , The entrance of the insert 2 has a conical shape 221, which creates a sealing seat, and the junction of the last bore 226 in the chamber of the rail has a rounded edge or a rounding 227 on.

The stepped bore 22 forms a throttle intended to attenuate the pressure waves (compression and depression) introduced into the high pressure fluid by the movements of closing and opening the injector.

The body 21 of the insert with its outer surface 23 of the insert 2 has a part with a large cross-section 231, which adjoins a part with a small cross-section 233 by a conical connection 232 which forms a bearing surface to the edge 1313 of the passage 131 of the connector. The outer surface 23 of the small section portion 233 terminates in a rounding 234. The large diameter of the portion 231 of the insert 2 is slightly smaller than that of the bore 1312 of the fitting 13. The small diameter of the portion 233 is significantly smaller than that of the bore 1314 of the fitting 13 downstream of the bore 1312, such that the insert 2 provided with the throttle can be easily installed in the passage 131 of the fitting 13 for mounting and the small cross-section part 233 is not in contact with the wall the passage 131 and in particular its bore 1314 is. Although it is not necessary for the hydraulic function, the stepped bore 1312/1314 allows the diameter of the bore to be reduced at the level of its intersection with the high pressure chamber 12. The length of the portion 233 of the insert 2 is smaller than the length of the bore 1314, such that the mouth of the throttle 226 is significantly removed from the mouth 1315 of the bore 1314 of the chamber 12.

This remark regarding the length of a part of the insert and the bore of the fitting can also be applied to the second embodiment, which will be described below.

The blocking of the insert 2 or its frictional arrangement is effected by autofrettage, as indicated below.

After the half-section of Figure 3, the rail 1, when it is equipped with all inserts with throttle 2, subjected to autofrettage. For this purpose, a closure, which is not shown, is applied to each connecting piece 13 against the conical seat 221 of the insert piece 2. In this way, the editions are created. The tension force F exerted in the axis xx during autofrettage establishes the tightness of the insert 2 (zone A) and also the tightness between the insert 2 and the passage 131 in the zone B by the contact between the conical surface 232 of the insert 2 and the edge 1313 of the connector 13th

In this way, the area of the bores 131 and the insert 2 is limited, which will be exposed to the Autof rettage- high pressure of the liquid which is introduced into the rail.

This exposed surface is the surface of the chamber 12 and the passage 131 of the connector 13 upstream (in the exiting direction of the high pressure fuel) in front of the insert 2, including the inner surface of the insert 2 and its outer surface upstream of the contact between its conical shoulder 232 and the Edge 1313 which separates the bore 1312 and the bore 1314 of the fitting 13. In other words, the surfaces opposite the insert 2 and the bore 1312 are not exposed to the high-pressure fluid of the autofrettage, but are subject to the forces generated by this high pressure. Thus, the very high Autofrettage- pressure plasticizes the inner layer of the exposed surface of the rail 1 and the insert 2, which is deformed to be pressed against the bore 1312 of the connector 13. After application of this very high autofrettage pressure, the fittings 13 pull together on each insert 2 which is shrunk thereby.

Figure 4 shows another embodiment of a rail la according to the invention, which is also on the conventional part of the rail with two fittings 13a, one is empty and the other has an insert with throttle 2a is limited. All of these fittings 13a preferably have the same structure so that their description will be limited to one of them.

The insert with throttle 2a is shown separately in section in FIG.

Referring to Figure 4 and the orientation which extends to the high pressure chamber 12a, the passage 131a in the fitting 13a is formed from an inlet cone 1311a followed by a conical chamber 1312a whose small base has a diameter larger than that of the downstream one Bore 1314a is to form an edge 1313a. The conical chamber 1312a forms a plug-in chamber of the "Morse taper" or equivalent cone type. The passage 131a receives the insert with throttle 2a of complementary shape by plugging. Referring to Figure 5, the insert with throttle 2a has a body 21a traversed by a stepped bore 22a formed by a series of decreasing diameter bores 222a, 224a, 226a separated by conical connections 223a, 225a. The entrance 221a of the insert 2a has a conical shape forming a sealing seat, and the mouth of the last bore 226a into the chamber 12a of the rail la has a rounded edge or fillet 227a. The stepped bore 22a forms a throttle, which is intended to attenuate the pressure waves, which are introduced into the high pressure fluid.

The outer surface 23a of the insert 2a has a large diameter conical portion 231a, the small base of which meets a small diameter cylindrical portion 233a through a conical connection 232a. The outer surface 23a terminates in a rounding 234a. The conical part 231a has a taper equal to that of the conical chamber 1312a of the fitting 13 and a cross section which can be received in the conical chamber 1312a by insertion so that the respective faces directly abut.

The cylindrical part 233a has a much smaller cross section than that of the bore 1314a of the fitting 13a.

After the half-section of Figure 6, the rail 1a, when equipped with all inserts with throttle 2a, is subjected to an autofrettage such as that described for the first embodiment shown in Figures 1-3.

To this end, a closure, not shown, is applied to each fitting 13a against the conical seat 221a of the inserts 2a to provide tightness with respect to the outside of the bore 22a and tightness between the conical surfaces of the parts 1312a and 231a.

For this purpose, a clamping force F is exerted on the ball, which is not shown, which is supported and creates a compression zone C. The force is transmitted to the conical contact zone between the conical portion 231a of the insert 2a and the conical surface of the chamber 1312a of the fitting 13a.

In this way, the area of the bores 131a and the insert 2a is limited, which will be exposed to the autofrettage high pressure of the liquid introduced into the rail. This exposed surface is upstream of the surface of the chamber 12a and the passage 131a of the fitting 13a (in the direction of discharge of the high-pressure fuel) in front of the insert 2a, including the inner surface of the insert 2a and its outer surface in advance of the contact between its conical surface 231a and Surface of the conical chamber 1312a. The cross section of the small base of the conical part 231a is larger than that of the small base of the conical chamber 1312a which meets the conical surface 1313a forming the shoulder so that the insert 2a can be clamped by insertion in combination with the autofrettage. without being in abutment against the shoulder 1313a, which would interfere or limit the insertion.

It will be appreciated that the conical surfaces of the parts 1312a or 231a could have grooves that enhance tightness during autofrettage and increase residual axial force between the two parts / surfaces.

The surfaces in contact with the insert 2a and the bore 1312a are not exposed to the high-pressure fluid of the autofrettage, but are subject to the generated forces. The very high autofrettage pressure plasticizes the inner layer of the exposed surface of the rail 1a and the insert 2a, which is deformed to be pressed against the bore 1312a of the fitting 13a. After application of this very high autofrettage pressure, the fittings 13a contract onto each insert 2a which is shrunk thereby.

The Rails 1, la forged steel has a minimum hardness of the order of 300 HB, which depends on the hardness of the piping heads and the properties that are compatible with the expected result of autofrettage.

The material of the insert 2, 2a has a hardness which is between 300 and 450 HV, in order to have sufficient plasticization during autofrettage and at the same time to maintain sufficient residual elasticity to ensure sufficient residual pressure between the insert 2, 2a and the rail 1 to show la.

The method for producing the rail 1, la according to the invention consists in:

Insert the insert 2, 2a with play and without having to exert a large force in the connector 13, 13 a,

to clamp the arrangement made in this way, to then have a pressure difference between the inner diameter and the outer diameter of the insert 2, 2a, and to produce a plastic deformation of the insert 2, 2a and the rail 1, la.

The plastic deformation ensures a residual contact between the insert with throttle 2, 2a and the rail 1, la.

The properties of the material of the insert with throttle are selected to ensure a sufficient residual force that keeps the insert 2, 2a in place during operation of the high-pressure accumulator 1, la of the injection system.

Nomenclature of the main elements without the suffixes "a ^" exceptions

Rail

11 body

12 high pressure chamber

13 connection piece

131 passage

1311 entry cone

1312 cylindrical chamber

1312a conical chamber

1313 sealing edge

1314 bore

132 External thread Insert with throttle

21 cylindrical body

21a conical body

22 stepped bore

221 entry cone

222 bore of large diameter

223 conical connection

224 bore of medium diameter

225 conical connection

226 bore with a small diameter

227 Rounding off

23 outer surface

231 large diameter cylindrical part 231a large diameter conical part

232 conical connection

233 cylindrical part with a small diameter

234 rounding off

Claims

claims

A high-pressure accumulator for a high-pressure injection system, which is formed by a cylindrical body (11) delimiting a high-pressure chamber (12, 12a) and connecting pieces (13, 13a) connected to outlet passages (131, 131a) which enter the high-pressure chamber (11). 12, 12a) are provided, wherein in at least one outlet passage (131, 131a), a throttle (22, 22a) is arranged to attenuate the pressure waves generated by the connecting piece (13, 13a) downstream injector,

characterized in that

the fitting (13, 13a) has at the outlet a passage (131, 131a) with a chamber (1312, 1312a) receiving an insert (2, 2a) provided with the throttle (22, 22a), and

the insert (2, 2a) is frictionally arranged in the chamber (1312, 1312a) by an auto-rettage process of the high-pressure accumulator.

2. High-pressure accumulator according to claim 1,

characterized in that

the passage (22, 22a) of the insert (2, 2a) has a rounding (227, 227a) at the mouth on the side of the high pressure chamber (12, 12a).

3. High-pressure accumulator according to claim 1,

characterized in that

the passage in the insert (2, 2a) is a stepped bore (22, 22a) formed by a series of decreasing diameter bores (222, 222a, 224, 224a, 226, 226a) defined by conical functions (223 , 223a, 225, 225a) are separated.

4. High-pressure accumulator according to claim 1,

characterized in that

the passage with the throttle (22, 22a) has a conical entrance (221, 221a) forming a sealing seat.

5. High-pressure accumulator according to claim 1,

characterized in that

the connecting piece (13, 13a) has a conical inlet (1311, 1311a).

6. High-pressure accumulator according to claim 1,

characterized in that

the chamber (1312) is cylindrical and forms with the bore (1314) a shoulder (1313) which creates a sealing edge,

- The insert (2) has an outer surface (23) with a cylindrical portion of large diameter to come in the assembly with play in the cylindrical chamber (1312), and a small diameter part (233), in the bore (1314) of the connecting piece (13) projects freely,

- Wherein the two parts (231, 233) of the insert (2) by a conical segment (233) are connected, which is intended to come against the edge (1313) of the connecting piece (13).

7. High-pressure accumulator according to claim 1,

characterized in that

- the fitting (13a) has a conical chamber (1312a) extending through a bore (1314a) having a cross-section smaller than that of the small base of the conical chamber (1312a), and

- The insert with throttle (2a) has a conical body (231a) with a length which is smaller than the length of the conical chamber (1312a), and the cross section of its small base larger than the cross section of the small base of the chamber (1312a) is

- wherein the taper of the chamber (1312a) and those of the conical body (231a) are identical.

8. High-pressure accumulator according to claim 7,

characterized in that

the surface of the conical chamber (1312a) and / or that of the conical body (231a) has inequalities, bumps and raised or recessed geometrical shapes to increase the tightness in the autofrettage in combination with the cone, which allows to ensure the contact pressure ,

9. High-pressure accumulator according to claim 1,

characterized in that

the cross-section of the part (233, 233a) of the insert (2, 2a) coming into the bore (1314, 1314a) is smaller than the cross-section of that bore, in order to prevent autofrettage of the rail (1, 1a) and the Insert (2, 2a) not to be in contact. High-pressure accumulator according to claim 1,

characterized in that

the length of the part (233, 233a) of the insert (2, 2a) is smaller than the length of the bore (1314, 1314a), such that the mouth of the throttle (226, 226a) is clearly away from the mouth of the

Bore (1314, 1314a) in the chamber (12, 12a) is removed.

Method for producing a high-pressure accumulator according to one of claims 1 to 10,

characterized in that

by milling, a chamber (1312, 1312a) is created in the exit passage (131, 131a) of each fitting (13, 13a),

- an insert piece (2, 2a) is created, which is crossed by a throttle (22, 22a), wherein the outer diameter of the insert is adapted to those of the chamber (1312, 1312a),

an insert (2, 2a) is installed in each chamber,

- The tightness of the inserts (2, 2a) and that of the entry of the connecting pieces (13, 13a) is created, and

- The thus assembled high pressure accumulator (1, la) is exposed to a car fret pressure to treat the inner surfaces of the high pressure accumulator and the inserts (2, 2a) in the chamber (1312, 1312a) of the fittings (13, 13a) non-positively to arrange.