FR3061934A1 - HIGH PRESSURE FUEL INJECTION SYSTEM RAMP - Google Patents

Abstract

Common rail for a high pressure injection system, formed of a cylindrical body (11) delimiting a high pressure chamber (12, 12a) and domes (13, 13a) provided with liquid outlet passages (131, 131a) high pressure opening into the chamber (12, 12a) with a throttle to attenuate the pressure waves generated by the injectors. The domes (13, 13a) each have a passage (131, 131a) with a chamber (1312, 1312a) receiving a sleeve (2, 2a) provided with a constriction (22, 22a), and the sleeve (2, 2a) is blocked in the chamber (1312, 1312a) by autofrettage of the ramp.

Description

Holder (s):

ROBERT BOSCH GMBH.

O Extension request (s):

® Agent (s): CABINET HERRBURGER.

* 54) HIGH PRESSURE FUEL INJECTION SYSTEM RAMP.

FR 3 061 934 - A1 (57) Common rail for a high pressure injection system, formed of a cylindrical body (11) delimiting a high pressure chamber (12, 12a) and domes (13, 13a) provided with passages (131, 131a) high pressure liquid outlet opening into the chamber (12, 12a) with a throttle to attenuate the pressure waves generated by the injectors. The domes (13, 13a) each have, at the outlet, a passage (131, 131a) with a chamber (1312,1312a) receiving a sleeve (2,2a) provided with a throttle (22, 22a), and the sleeve (2, 2a) is blocked in the chamber (1312, 1312a) by the autofrettage of the ramp.

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Field of the invention

The present invention relates to a common rail for a high pressure injection system, formed of a cylindrical body delimiting a high pressure chamber and domes provided with high pressure liquid outlet passages opening into the chamber with a constriction to attenuate the pressure waves generated by the injectors.

State of the art

There is already known such a ramp of a high pressure injection system shown in FIG. 7. This ramp 100, also called “common rail”, is constituted by a cylindrical body 111 made of thick forged steel, surrounding a high pressure chamber 112. The boom body has outlet domes 113 for connecting the high pressure lines each connected to an injector. These domes 113 are traversed by a bore 114 opening into the chamber 112. At the bottom of the bore at the junction with the chamber, there is a pierced constriction 115. This constriction 115 damps the pressure waves generated by the obturation movements of the injector associated with each dome in the high pressure liquid of the boom. The throttle 115 produced by the drilling is sometimes called a "nozzle".

This solution certainly makes it possible to damp the pressure waves but it has a certain number of drawbacks, in particular its effectiveness is relatively reduced because the drilling forming this constriction does not allow elaborate geometric shapes to be produced.

It is also not possible to meet strict tolerances; moreover, at the outlet of the passage in the chamber, the realization in the form of a hole generates an edge which generates strong dispersions in the damping of the waves. To avoid this, you need an electrochemical finish on the edge of the hole in the hole to round it off and remove any burrs, or even a protruding part in the chamber, which is a delicate and therefore expensive operation.

According to the state of the art, there are also alternatives to sprinklers drilled in the rail in the form of fitted sprinklers. These sprinklers are fitted in the traditional way, that is to say by mastering the negative geometric play (geometric tightening) and the use of a press by monitoring the fitting efforts. These fitted sprinklers are only used for rails without autofrettage or with moderate autofrettage because autofrettage causes residual deformations which make mastering the geometric tightening too critical. In this case, an additional costly retouching of the fitting diameter would be necessary after the autofrettage. This known solution therefore has many drawbacks.

Purpose of the invention

The object of the present invention is to develop a common rail for a high pressure injection system making it possible to effectively dampen the pressure waves generated in the rail by closing the injection valves while having a simple embodiment and generating a low dispersion. damping between nozzles of the same rail or different rails.

Presentation and advantages of the invention

To this end, the subject of the present invention is a common rail for a high pressure injection system of an internal combustion engine formed by a cylindrical body delimiting a high pressure chamber and domes provided with high pressure liquid outlet passages opening out. in the chamber with a throttle to attenuate the pressure waves generated by the injectors. The domes each have a passage at the outlet with a chamber receiving a sleeve provided with a throttle, and the sleeve is blocked in the chamber by the autofrettage of the ramp.

The ramp according to the invention is simple and precise to manufacture for throttling. The joining of the sleeves in the ramp is done simply and without requiring new or different means since this joining is done by the autofrettage of the ramp, the autofrettage of the ramp whose pressure of use justifies this technique in order to ensure the fatigue strength of the ramp. This does not lengthen the manufacturing cycle.

The constriction made outside the ramp allows simple manufacturing by drilling and finishing operations, outside the ramp without the risk of introducing foreign bodies into the ramp and avoiding any problem of burrs; on the contrary, it allows the creation of smooth edges or leaves.

Thus, the passage of the sleeve includes a leave at the outlet on the high pressure chamber side.

According to another advantageous characteristic, the passage in the sleeve is a stepped hole formed by a succession of holes of decreasing diameter separated by conical functions. There is thus a stepped throttle, allowing better optimization of the sleeve with respect to the damping / loss of system efficiency compromise.

The succession of holes with decreasing diameter is just one example of complex geometry allowed by a nozzle machined separately from the ramp. The aim is to obtain an asymmetry of the pressure drop, that is to say less pressure drop in the direction useful for injection and more pressure drop in the direction contributing only to the amortization.

According to another characteristic, the throttle passage has a conical inlet forming a sealing seat for the autofrettage operation.

According to another characteristic, the dome has a conical entry, again for sealing for autofrettage.

According to a more particular characteristic, the chamber is cylindrical and forms with the bore a shoulder providing a sealing edge, the sleeve has an outer surface with a cylindrical part of large diameter to come into the cylindrical chamber with clearance during assembly and a part of small diameter freely projecting into the bore of the dome, the two parts of the sleeve being connected by a conical segment intended to come against the edge of the dome.

According to another characteristic, the dome comprises a conical chamber continuing with a drilling of section smaller than that of the small base of the conical chamber, and the throttling sleeve has a conical body of length less than the length of the conical chamber and the section of its small base is greater than the section of the small base of the chamber, the conicity of the chamber and that of the conical body being identical.

In the case of the conical chamber, advantageously, the surface of the conical chamber and / or that of the conical body has inequalities, asperities and geometric shapes in relief or in hollow to increase the attachment of the two surfaces in contact by autofrettage and also better sealing during autofrettage.

According to another characteristic, the section of the part of the sleeve coming into the bore is smaller than the section of this bore so as not to be in contact with the latter after autofrettage of the ramp and the sleeves.

The connection surface between the sleeve and the dome is thus reduced by the single contact surface which can be tightened by autofrettage.

According to another characteristic, the length of the part of the sleeve is less than the length of the bore so that the outlet of the throttle is clearly distant from the outlet of the bore in the chamber. Thus, the outlet of the hole in the sleeve will be far above the outlet of the hole in the chamber and influences the pressure drop.

The subject of the invention is also the production of a common ramp as defined above, this process being characterized in that a chamber is produced by machining in the outlet passage of each dome, a sleeve is traversed by a constriction, the outside diameter of the sleeve being adapted to that of the chamber, a sleeve is installed in each chamber, the sleeve and the entrance to the dome are sealed, and the rail thus assembled is subjected to pressure autofrettage to treat the interior surface of the ramp and block the sleeves in the domes chamber.

As already indicated above, the method of making the ramp is particularly simple while offering the advantage of being able to carry out precise and effective throttles for damping shock waves (water hammer).

Drawings

The present invention will be described below in more detail with the aid of exemplary embodiments shown in the accompanying drawings in which:

Figure 1 is an axial sectional view of part of a common rail of a high pressure injection system, Figure 2 is an axial sectional view of a throttle sleeve for the common rail of Figure 1, FIG. 3 is a schematic view in half-section of the embodiment of the ramp of FIG. 1, FIG. 4 is a view in axial section of another embodiment of a ramp of the injection system according to the invention, FIG. 5 is an axial section of the throttle sleeve for the common rail of FIG. 4, FIG. 6 is a half-section view explaining the mounting of the throttle sleeve in a dome of the rail of FIG. 4, Figure 7 is a sectional view of a known ramp.

Description of embodiments of the invention

According to Figure 1, the invention relates to a ramp 1 of a high pressure injection installation in an internal combustion engine. A current part of this ramp is shown in axial section. The other components of the injection system are not shown.

The ramp 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 to distribute the high pressure fuel to the injection valves (injectors) controlled by the unit. engine management unit.

The closing and opening movement of the injectors produces compression and vacuum waves ("water hammer") transmitted by the high pressure liquid in the pipe connecting the injector to the ramp 1 and thus arriving in the ramp.

The cylindrical body 11 has connection domes 13 each connected by a passage 131 to the high pressure chamber 12 and by a high pressure pipe to its injector. Externally, the dome has a thread 132 for screwing the connection of the high pressure pipe.

The example in Figure 1 is limited to representing the current part of the ramp with two domes 13, one empty, the other occupied by a throttle sleeve 2. The ramp 1 has as many domes 13 and outputs high pressure fuel that there are injectors supplied. All these domes 13 have the same structure and the description below will be limited to one of them.

The dome 13 on the right of FIG. 1 shows its passage 131 without its throttling sleeve 2; the dome 13 on the left is equipped with the throttling sleeve 2.

The throttle sleeve 2 is shown in section separately in FIG. 2.

According to FIG. 1, the passage 131 in a dome 13 consists, according to the orientation going towards the high pressure chamber 12, of an inlet cone 1311 followed by a cylindrical chamber / bore 1312 of diameter greater than that of drilling 1314 downstream to form a sealing edge 1313. The passage 131 receives the throttle sleeve 2.

According to FIG. 2, the throttle sleeve 2 has a cylindrical body 21 crossed by a stepped bore 22 formed by a succession of drillings of decreasing diameters 222, 224, 226, separated by conical junctions 223, 225. The inlet of the sleeve 2 has a conical shape 221 providing a sealing seat and the outlet of the last hole 226 in the chamber of the ramp has a rounded edge or a leave 227.

The stepped bore 22 constitutes a constriction intended to attenuate the pressure waves (compression and depression) induced in the high pressure liquid by the closing and opening movements of the injector.

The body 21 of the sleeve with its outer surface 23 of the sleeve 2 has a part of large section 231 joining a part of small section 233 by a conical junction 232 constituting a bearing surface to cooperate with the edge 1313 of the passage 131 of the dome . The outer surface 23 of the portion 233 of small section ends in a fillet 234. The large diameter of the portion 231 of the sleeve 2 is slightly less than that of the bore 1312 of the dome 13 and the small diameter of the portion 233 is significantly lower than that of the bore 1314 of the dome 13 downstream of the bore 1312 so that for mounting, the sleeve 2 provided with the throttle installs effortlessly in the passage 131 of the dome 13 and the part 233 of small section is not in contact with the wall of passage 131 and in particular its bore 1314. The stepped bore 1312/1314 although not necessary for the hydraulic function makes it possible to reduce the diameter of the bore at its intersection with the high pressure chamber 12. The length of the part 233 of the sleeve 2 is less than the length of the bore 1314 so that the outlet of the throttle 226 is clearly distant from the outlet 1315 of the bore 1314 of the chamber 12.

This remark concerning the length of a part of the sleeve and of the bore of the dome also applies to the second embodiment which will be described later.

The sleeve 2 is blocked by an autofrettage as indicated below.

According to the half-section of Figure 3, when the ramp 1 is equipped with all the throttle sleeves 2, it is subjected to autofrettage. For this, a shutter (not shown) is applied to each dome 13 against the conical seat 221 of the sleeve 2. Support is thus produced. The clamping force F exerted in the axis xx during the autofrettage seals the sleeve 2 (zone A) and also the seal between the sleeve 2 and the passage 131 in the zone B, by the contact between the surface conical 232 of the sleeve 2 and of the edge 1313 of the dome 13.

This delimits the surface of the holes 131 and the sleeves 2 which will be exposed to the high autofretting pressure of the liquid introduced into the ramp.

This exposed surface is the surface of the chamber 12 and of the passage 131 of the domes 13 upstream (in the direction leaving the high pressure fuel) of the sleeve 2, including the internal surface of the sleeve 2 and its external surface upstream of the contact between its conical shoulder 232 and the edge 1313 separating the bore 1312 and the bore 1314 of the dome 13. In other words, the facing surfaces of the sleeve 2 and of the bore 1312 are not exposed to the liquid at high autofrettage pressure but undergo the forces generated by this high pressure. Thus, the very high autofrettage pressure plasticizes the inner layer of the exposed surface of the ramp 1 and the sleeve 2 which is deformed to be pressed against the bore 1312 of the dome

13. After the application of this very high autofrettage pressure, the domes 13 retract on each sleeve 2 which is thus shrunk.

FIG. 4 shows another embodiment of a ramp 1a according to the invention, also limited to the current part of the ramp with two domes 13a, one empty and the other occupied by a throttle sleeve 2a. All the domes 13a have the same structure so that their description will be limited to one of them.

The throttle sleeve 2a is shown in section, separately in FIG. 5.

According to FIG. 4 and the orientation going towards the high pressure chamber 12a, the passage 131a in the dome 13a consists of an inlet cone 1311a followed by a conical chamber 1312a whose small base has a diameter greater than that of the hole 1314a downstream, to form an edge 1313a. The conical chamber 1312a forms a fitting chamber of the "Morse cone" or equivalent cone type. The passage 131a receives by fitting the throttle sleeve 2a of complementary shape.

According to FIG. 5, the constriction sleeve 2a has a body 21a crossed by a stepped bore 22a formed by a succession of drillings of decreasing diameters 222a, 224a, 226a, separated by conical junctions 223a, 225a. The inlet 221a of the sleeve 2a is of conical shape providing a sealing seat and the outlet of the last bore 226a in the chamber 12a of the ramp 1a has a rounded edge or a leave 227a. The stepped bore 22a constitutes a constriction intended to attenuate the pressure waves induced in the high pressure liquid.

The outer surface 23a of the sleeve 2a has a conical part 231a of large diameter whose small base joins a cylindrical part 233a of small diameter by a conical junction 232a. The outer surface 23a ends in a fillet 234a. The conical part 231a has a conicity equal to that of the conical chamber 1312a of the dome 13 and a section to be received in the conical chamber 1312a by fitting so that the respective surfaces are in good contact.

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

According to the half-section of FIG. 6, when the ramp 1a is equipped with all the throttle sleeves 2a, it is subjected to autofrettage as has been described for the first embodiment shown in FIGS. 1-3.

For this, a shutter (not shown) is applied to each dome 13a against the conical seat 221a of the sleeve 2a in order to seal against the outside of the bore 22a and to seal between the conical surfaces of the parts 1312a and 231a.

For this, a clamping force F is exerted on the ball (not shown) which rests and creates a compression zone C. The force is transmitted to the conical contact zone between the conical part 231a of the sleeve 2a and the conical surface of chamber 1312a of dome 13a.

This delimits the surface of the holes 131a and of the sleeves 2a which will be exposed to the high autofretting pressure of the liquid introduced into the ramp.

This exposed surface is the surface of the chamber 12a and of the passage 131a of the domes 13a upstream (in the direction coming out of the high pressure fuel) of the sleeve 2a, including the internal surface of the sleeve 2a and its external surface upstream of the contact between its conical surface 231a and the surface of the conical chamber 1312a. The section of the small base of the conical part 231a is greater than that of the small base of the conical chamber 1312a joining the conical surface 1313a forming the shoulder so that the sleeve 2a can be tightened by fitting combined with ofο autofrettage without being in abutment against the shoulder 1313a, which would hinder or limit the fitting.

It should be noted that the conical surfaces of the parts 1312a or 231a could have grooves strengthening the seal during the autofrettage and increasing the residual axial force between the two parts / surfaces.

The contact surfaces of the sleeve 2a and the bore 1312a are not exposed to the high pressure autofrettage liquid but undergo the forces generated. The very high autofrettage pressure plasticizes the inner layer of the exposed surface of the ramp 1a and the sleeve 2a which is deformed to be pressed against the bore 1312a of the dome 13a. After the application of this very high autofrettage pressure, the domes 13a retract on each sleeve 2a which is thus shrunk.

The forged steel of the ramps 1 has a minimum hardness of the order of 300 HB depending on the hardness of the pipe heads and characteristics compatible with the expected result of autofrettage.

The material of the sleeve 2, 2a has a hardness of between 300 and 450 HV to have sufficient plasticization during the autofrettage while retaining sufficient residual elasticity to have sufficient residual pressure between the sleeve 2, 2a and the ramp 1, the.

The process for producing the ramp 1, the according to the invention consists in:

place the sleeve 2, 2a in the dome 13, 13a with play and without having to exert a significant force, tighten the assembly thus produced to then have a pressure difference between the inside diameter and the outside diameter of the sleeve 2, 2a , and produce a plastic deformation of the sleeve 2, 2a and of the ramp 1, la.

The plastic deformation ensures the residual contact between the throttling sleeve 2, 2a and the ramp 1, la.

The material properties of the throttle sleeve are chosen to guarantee a sufficient residual force keeping the sleeve 2, 2a in place during the operation of the common rail 1, the of the injection system.

Nomenclature of main elements without the suffixes "a" except in exceptional cases

Ramp

Body

High pressure chamber

Dome

131 Passage

1311 Entrance cone

1312 Cylindrical chamber

1312a Conical chamber

1313 Sealing edge

1314 Drilling

132 External thread

Throttle sleeve

Cylindrical body

21a Conical body

Staged drilling

221 Entrance cone

222 Large diameter drilling

223 Conical junction

224 Intermediate diameter drilling

225 Conical junction

226 Small diameter drilling

227 Leave

External surface

231 Large diameter cylindrical part

231a Large diameter conical part

232 Conical junction

233 Small diameter cylindrical part

234 Leave

Claims (11)

1 °) Common rail for a high pressure injection system, formed of a cylindrical body (11) delimiting a high pressure chamber (12, 12a) and domes (13, 13a) provided with passages (131, 131a) of high pressure liquid outlet opening into the chamber (12, 12a) with a constriction to attenuate the pressure waves generated by the injectors, common rail characterized in that the domes (13, 13a) each have a passage ( 131, 131a) with a chamber (1312, 1312a) receiving a sleeve (2, 2a) provided with a throttle (22, 22a), and the sleeve (2, 2a) is locked in the chamber (1312, 1312a) by autofrettement of the ramp. 2) common rail according to claim 1, characterized in that the passage (22, 22a) of the sleeve (2, 2a) includes a leave (227, 227a) at the outlet on the high pressure chamber side. 3) common rail according to claim 1, characterized in that the passage in the sleeve (2, 2a) is a stepped bore (22, 22a) formed by a succession of drillings of decreasing diameter (222, 222a, 224, 224a, 226, 226a) separated by conical functions (223, 223a, 225, 225a). 4 °) common rail according to claim 1, characterized in that the passage with the throttle (22, 22a) has a conical inlet (221, 221a) forming a sealing seat. 5 °) common ramp according to claim 1, characterized in that the dome (13, 13a) has a conical inlet (1311, 1311a). 6 °) common rail according to claim 1, characterized in that the chamber (1312) is cylindrical and forms with the bore (1314) a shoulder (1313) providing a sealing edge, the sleeve (2) has an outer surface (23) with a cylindrical part of large diameter to come into the cylindrical chamber (1312) with clearance during assembly and a part of small diameter (233) freely projecting in the bore (1314) of the dome (13), the two parts (231, 233) of the sleeve (2) being connected by a conical segment (233) intended to come against the edge (1313) of the dome (13). 7 °) common rail according to claim 1, characterized in that the dome (13a) comprises a conical chamber (1312a) continuing with a bore (1314a) of section smaller than that of the small base of the conical chamber (1312a) , and the throttle sleeve (2a) has a conical body (231a) of length less than the length of the conical chamber (1312a) and the section of its small base is greater than the section of the small base of the chamber (1312a ), the conicity of the chamber (1312a) and that of the conical body (231a) being identical. 8 °) common rail according to claim 7, characterized in that the surface of the conical chamber (1312a) and / or that of the conical body (231a) has inequalities, roughness and geometric shapes in relief or hollow to increase the tightness during autofrettage in combination with the cone to ensure contact pressure. 9 °) common ramp according to claim 1, characterized in that the section of the part (233, 233a) of the sleeve (2, 2a) coming into the bore (1314, 1314a) is less than the section of this bore so as not to not be in contact with it after autofrettage of the ramp (1, la) and the sleeves (2, 2a). 10 °) common rail according to claim 1, characterized in that the length of the part (233, 233a) of the sleeve (2, 2a) is less than the length of the bore (1314, 1314a) so that the outlet of the 'throttle (226, 226a) is clearly distant from the opening of the bore (1314, 1314a) in the chamber (12, 12a). 11 °) Method for producing a common rail according to one of claims 1 to 10, characterized in that a chamber (1312, 1312a) is produced by machining in the outlet passage (131, 131a) of each dome (13, 13a), a sleeve (2, 2a) is made through which a throttle (22, 22a) passes, the outside diameter of the sleeve being adapted to that of the chamber (1312, 1312a), a sleeve (2, 2a) in each chamber, the sleeve (2, 2a) and that of the dome inlet (13, 13a) are sealed, and the ramp (1, la) thus assembled is subjected to an autofrettage pressure to treat the interior surface of the ramp and block the sleeves (2, 2a) in the chamber (1312, 1312a) of the domes (13, 13a). 1/3