CA2251148A1

CA2251148A1 - Common-rail injection system

Info

Publication number: CA2251148A1
Application number: CA002251148A
Authority: CA
Inventors: Fritz Spinnler
Original assignee: Schweizerische Industrie Gesellschaft
Current assignee: Schweizerische Industrie Gesellschaft
Priority date: 1997-11-05
Filing date: 1998-10-19
Publication date: 1999-05-05
Also published as: EP0915252A2; JPH11200986A; EP0915252A3

Abstract

A common-rail injection system (8) for internal combustion engines (10) operates with a rail (12) which is arranged parallel to a cylinder head housing (14) and has a pressure space (20) and openings (22) for receiving injectors (24). The injectors (24) are fitted into the openings (22) of the rail (12) in such a way that they can be inserted through the openings (22) into the injector openings (44), lying in the extension of the openings (22), of the cylinder head housing (14). In the region of the pressure space (20) of the rail (12), each injector (24) has an inlet opening (38) through which the pressure medium can flow directly from the pressure space (20) into the injector (24). The rail (12) can be connected to an outlet of the high-pressure pump 16 via further components or directly.

Description

CA 022~1148 1998-10-19 TITT F OF TT-TF TNVFNTION
COMMON-RAIL INJECTION SYSTEM

T~ACK(~ROUNn OF TT-TF INVFNTTON
Fielll of the Tnvention The invention relates to a common-rail injection system for intern~l combustion engines.

nescription of the Rel~t~ ~rt Common-rail injection systems are used in internal combustion engines in which, in order to optimize the combustion performance, the combustion medium is to be finely atomized in the combustion chambers of the individual cylinders. For this purpose, the combustion medium is colllplessed in a high-pres~ule pump and distributed to the injectors of the individual cylinders via a rail. Finally, the process of injecting the combustion medium into the combustion chamber is triggered via an electrical signal, the combustion medium which is under high pressure being distributed finely in the combustion chambers of the engine at high speed via the injection nozzles of the injectors.
An injection system of this type is disclosed, for example, in CH patent application No. 1997 1275/97. A high-ples~ule pump which has a pump housing is mounted on an engine housing of an internal combustion engine via a flange. The high-ples~u~e pump operates with a plunger cylinder which, together with a plunger piston, bounds a delivery space. The delivery space is connected to a line for the inflow of the pressure medium which is regulated by a ples~u-e-controlled inlet valve, and the plunger cylinder has a passage opening for the pressure medium to flow out, said flow also being regulated by a pressure-CA 022~1148 1998-10-19 controlled valve. The plunger cylinder is surrounded by a pressure element whose flow ducts connect the passage opening of the plunger cylinder to the outside. The flow ducts of the plcs~ule element are connected to the prcs~ulc space of the rail via a high-ples~urc hose between the ples~ulc element and common rail or by virtue of the fact that the common rail is formed directly onto the plCS~ulc element. The connection between the individual injectors and the rail is provided by high-plcs~ulc hoses which are attached to the injectors and/or the rail by al~plu~liate connecting elements. As a result of its separate pump housing and the variety of connecting elements and connections, this design has a large number of, in certain cases, extremely expensive parts which have to be fitted together in complex assembly oper-ations.
JP-A-09 060562 discloses an int~ l combustion engine with direct injection, in which engine a high-plcs~ule fuel pump is connected to the cylinder head. The cylinder head has in its interior a duct through which the fuel is conveyed away from the high-pressure fuel pump. The common rail which is fitted onto the injection valves is connected to the cylinder head and has in its interior a passage for distributing the fuel to the injection valves.
In the design known from US patent No. 5,603,303, a pump housing for a high-pres~ulc pump is formed from a plunger cylinder and a piston guide. This pump housing which is composed of a plunger cylinder and piston guide engages through an engine housing, in a suitable opening, in such a way that part of the pump housing projects out of the engine housing and is attached directly to it by means of bolts. This design is also complex in terms of design and assembly.

~UMMARY OF T~F TNVFNTTON

CA 022~1148 1998-10-19 It is an object of the present invention to provide a common-rail injection system which has an improved and, in particular, more simple design.
This and other objects are achieved by means of a common-rail injection system for an intçrn~l combustion engine, comprising a rail having a pres~ule space and injector openings connected to said p~S~ space, wherein the rail also has a fitting opening; fuel injectors received in said injector openings; and a plunger cylinder of a high pleS~Ille pump received in said fitting opening, said plunger cylinder having a delivery space receiving a fuel to be injected, and a passage co,ll",ullicating with said pleS~ e space of said rail so that said high-pres~ule pump pumps the fuel from said delivery space to the pleS~iule space of the rail via the passage.
According to the invention, the elongated rail is connected to the high-pressure pump and has a pres~u~e space along its longitu~lin~l axis. Openings penetrating the pressure space are provided for directly receivillg injectors. The advantage of such a design is that the injectors can be inserted directly into the rail, which makes assembly much easier. A further simplification is provided by the insertion of a plunger cylinder into a fitting opening of the rail which is provided for this purpose. If the plunger cylinder is secured in the fitting opening of the rail by means of a press fit, this acts in the same way as the arrangement in which it is surrounded by a pleS~UIt; element, which arrangement is described in said CH
1997 1275/97. As is there stated, the arrangement in which the plunger cylinders are surrounded by a pressure element can provide various advantages such as the loading of the high-ples~ pump with higher pl'eS~I~'eS, for example.
In a preferred embodiment, the inserted injectors have, in the region of the pres~e space of the rail after the insertion, inlet openings through which the pres~u~c medium can flow into the injectors and be injected from there into the combustion chambers. The CA 022~1148 1998-10-19 advantage lies in the fact that the plC;S~UIc medium can flow from the pres~ulc chamber of the rail directly into the injectors. Assembly is therefore much simpler and there can be a saving in terms of m~teri~l costs due to the elimin~tion of the connecting parts.
In a particularly simple embodiment, the openings for the injectors in the rail are aligned with their opening axes parallel to one another and preferably lie in a plane. As a result, the provision of the openings for the injectors both in the rail and in the cylinder head housing and the insertion of the injectors into the openings are made easier. This is highly significant for industrial series production.
The parallel axial alignment of the fitting opening of the plunger cylinder, and of the openings for the injectors in turn simplifies the provision of the openings and the assembly of the entire system. Furthermore, this permits the rail to be of linear design.
The injection system can be simplified further if the rail forms part of the pump housing, in particular if it is integrally formed onto the pump housing and/or the housing cover. In addition to very simple assembly and simple design, the integration of the pump housing of the high-plcs~Ll~c pump into an engine housing, preferably into a cylinder head housing of an intern~l combustion engine, can allow a weight saving to be achieved.

RRTFF nF~scRTpTloN OF T~TF nR ~
The common-rail injection system according to the invention will now be explained in more detail with reference to the attached drawings, in which:
Fig. 1 shows a longitudinal section of part of a common-rail injection system according to the invention;
Fig. 2 shows the injection system of Fig. 1 in a section along the line II-II; and;
Fig. 3 shows the injection system of Fig. 1 in a section along the line III-III, with an CA 022~1148 1998-10-19 int~.rn~l combustion engine which is illustrated partially in section.

nFTATT Fn nF~CRTPTION OF T~F T)RAWrN(~
That part of the inventive common-rail injection system 8 according to the invention of an int~rn~l combustion engine 10 (also illustrated in basic form in Figs 2 and 3) which is illustrated in Fig. 1 shows an elongated, linear rail 12 which is arranged parallel to a cylinder head housing 14 which is associated with the internal combustion engine 10, and a high-pres~ule pump 16 whose drive is provided in a known fashion (described in more detail below) by the internal combustion engine 10.
Along its longitudinal axis 18, the rail has a l)res~ule space 20 and, perpendicularly thereto, openings 22 penetrating the rail 12 in the region of the pressule space 20 for receiving injectors 24. The openings 22 are arranged with their opening axes 26 parallel to one another and lie in a plane. In their extension, the opening axes 26 also form the axes of injector openings 28 of the cylinder head housing 14. The injectors 24 thus also lie with their injector axes 26a parallel to one another and in a plane when they are inserted through the openings 22 of the rail 12 into the injector openings 28 of the cylinder head housing 14.
As illustrated in Figs. 1 and 2, the injectors 24, which are of essentially rotationally symmetrical design, have injection nozzles 30 at one end. The injectors 24 are shaped in such a way that, after assembly, the injection nozzles 30 project into the combustion chamber 32 (illustrated in Fig. 2) of the int~rn~l combustion engine 10. An injector head 34 which lies opposite the injection nozzle 30 projects beyond the rail 12. As is shown by Fig. 1, the injectors 24 have, in the section which is located within the ples~ e space 20 of the rail 12 after the insertion of the injectors 24, a circumferential groove 36 which ensures that the pl'~s~ule medium located in the pressure space 20 can flow around the injectors 24. In this CA 022~1148 1998-10-19 portion of the injectors 24 there are also inlet openings 38 through which the plCS~ulc medium can flow into the injectors 24. The injectors 24 are secured in the rail 12 by an ~chment element 40, for example a screwed connection, in the region of the injector head 34 which projects beyond the rail 12, and by an abutment 42 on the opposite outer wall of the rail 12.
On the side of the high-ples~ule pump 16, the rail 12 has two fitting openings 44 for receiving plunger cylinders 46, and a duct 20a. At the dashed line 48, the duct 20a merges with the prcs~ulc space 20 of the rail 12 and connects the fitting openings 44 to the pres~ulc space 20 of the rail 12. So that the plCS~ulc medium can flow around the inserted plunger cylinders 46, annular circumferential grooves are formed in the plunger cylinders 46 at the channel 20a, which grooves form, when the plunger cylinders 46 are inserted, an annular duct 50 (indicated by dashed lines) around the plunger cylinders 46. The plunger cylinders 46 are secured in the rail 12 by means of a press fit, and this has the same effect as the arrangement in which the plunger cylinders are surrounded by a p~cs~u,e element, as is described in CH
1997 1275/97.
The fitting openings 44 provided in the rail 12 for the plunger cylinders 46 have axes 52 which lie parallel to one another and which are arranged in a plane with and parallel to the opening axes 26 of the openings 22 in the rail 12 or the injector axes 26a of the injectors 24.
The result is that after their insertion into the fitting openings 44, the plunger axes 52a of the plunger cylinders 46 are also parallel to and in a plane with the opening axes 26 and/or the injector axes 26a.
Each plunger cylinder 46 bounds, together with a plunger piston 54, a delivery space 56. This delivery space 56 is connected to a reservoir (not illustrated) for the pressure medium via an inflow duct 58 which enters the plunger cylinder 46 and a feedline 58a. The CA 022~1148 1998-10-19 inflow of the plGs~ule medium is regulated by a ples~ulG-controlled inlet valve 60. The plG~UlG medium can flow out of the delivery space 56, regulated by a pre~ G-controlled outlet valve 64, via a passage 62 in the plunger cylinder 46, and connects the delivery space 56 to the annular duct 50.
The high-ples~ulG pump 16 has a pump housing 66, which is associated, inter alia, with a housing element 68 having an end wall 68a in which there are housing openings 70.
The plunger cylinders 46 project, with the side in which the plunger pistons 54 lead into the plunger cylinders 46, into these housing openings 70 of the side wall 68a of the housing element 68. The housing openings 70 are designed such that a small gap 72 remains between the inserted plunger cylinders 46 and the housing element 68, so that the plunger cylinders 46 can be inserted into the housing element 68 with a certain degree of play. The housing element 68 is open to the outside by way of the gaps 72 and by way of the side wall 68a. The housing element 68 is closed off and covered by the rail 12 which is arranged directly adjoining on the side wall 68a of the housing element 68.
In a wall 74 (lying perpendicular to this side wall 68a) of the housing element 68 there is a recess 76 formed as an internal bearing, in which recess the driveshaft 78 is mounted at its end region 78a lying opposite the power tr~n~mic~ion means. On the other side, the wall 74 merges with the integrally formed cylinder head housing 14 at the dashed dividing line 74a. Opposite the wall 74 of the housing element 68, a side plate 80, which is also associated with the pump housing 66, closes off a further opening of the housing element 68. In a bearing opening 82 of this side plate 80, the driveshaft 78 is mounted on its side facing the power tr~n~mi~sion means. In the case of repairs, access into the interior of the pump housing 66 is also made possible by means of this side plate 80.
The plunger cylinders 46 with the plunger pistons 54, and the driveshaft 78 of the CA 022~1148 1998-10-19 high-plcssu~c pump 16 are arranged at right angles to one another. For the reciprocating movement of the plunger pistons 54 -- forced in the direction of the driveshaft 78 by com-pression springs 83 -- in the plunger cylinders 46 of the high-pres~ule pump 16, eccentric cams 84 are mounted on the driveshaft 78 ofthe high-plcs~c pump 16. Rolling rings 86 which can rotate freely on the eccentric cams 84 are mounted in the known fashion between the eccentric cams 84 and the plunger pistons 54. To drive the high-~cs~ule pump 16 in this embodiment, the driveshaft 78 is coupled, via a spur gear 88 (schem~tically illustrated), to a (schem~tically illustrated) c~m.ch~c 90 of the internal combustion engine 10.
As best seen in Fig. 2, the injector 24 is secured in the rail 12 by the attachment element 40 and the abutment 42 and is inserted into the injector opening 28 of the cylinder head housing 14. The intern~l combustion engine 10 which is shown only schematically in Fig. 3 and which has an only partially illustrated engine housing 92, is a reciprocating piston engine in whose piston 94 there is a combustion chamber 32. The injection nozzle 30 of the injector 24 projects into this combustion chamber 32. The piston 94 is connected via a crank gear 96 to a cr~nk~h~ 98, of which connection only a schematic illustration is made.
As seen in Fig. 3, the circumference 100 and the arrows 102 indicate the tr~n~mi~ion of power from the c~nn~h~ft 90 to the driveshaft 78 of the high-pressure pump 16 via the spur gears 88. Arranged at right angles to the driveshaft 78 is the plunger cylinder 46 which is surrounded by the rail 12 and provided with the feedline 58a for the inflow of the ples~ule medlum.
For the method of operation of the injection system 8 it is advantageous but not necessary that the rotary movement of the driveshaft 78 and that of the c~m~h~ft 90 of the internal combustion engine 10 are operated at synchronized angles. Preferably, the driveshaft 78 is driven in a known manner from the c~m~h~ft 90, as shown in Figs. 1 and 3, via the spur CA 022~1148 1998-10-19 gear 88, for example. Owing to the rotary movement of the driveshaft 78, via the eccentric cam 84, the plunger pistons 54 execute rotary movements. During an intake stroke of the plunger piston 54, the inlet valve 60 opens under the control of pl'eS~ e, and the pleS~Ulc medium flows out of the reservoir into the delivery space 56 via the feedline 58a and the inflow duct 58. During a conlples~ion stroke of the plunger piston 54, the inlet valve 60 closes and the outlet valve 64 opens under the control of pleS~iUlt; and clears the passage 62.
The ples~ule medium can thus flow out of the delivery space 56 via the passage 62 into the annular duct 50 and on into the duct 20a of the rail 12. From there, it flows on into the pres~ule space 20 of the rail 12 and through the inlet openings 38 into the interior of the injectors 24. When an injection is triggered by an electric signal, the pressure medium is distributed finely into the combustion chamber 32 at high speed and high ples~u~e.
Possible ways of providing drive other than as described above from the c~m~h~L 90 to the driveshaft 78 via a spur gear 88 are of course also possible. Thus, instead of a spur gear 88, it is, for example, conceivable to transmit power via a belt drive or drive can be provided directly from the cr~T-k~h~[ 98 instead of from the c~ h~ 90.
In a different embodiment, instead of the rail 12, a housing cover 106 is arranged directly adjoining the side wall 68a of the housing element 68 and the housing element 68 which is open by way of the gaps 72 between the inserted plunger cylinders 46 and the housing element 68 is closed off in this way. For this purpose, the housing cover 106 must have, in the same way as the rail 12, fitting openings 44 for receiving the plunger cylinders 46 and a duct 20a. As in the rail 12 and also in the housing cover 106, the plunger cylinders 46 which are inserted with a press fit are configured such that each delivery space 56 is connected to the duct 20a of the housing cover 106 via the passage 62 and the annular duct 50 formed by the annular groove on the plunger cylinder 46. The component which contains the CA 022~1148 1998-10-19 plunger cylinders 46 and which is arranged directly adjoining the housing element 68 in Fig.
1 may therefore also be the housing cover 106 onto which the rail 12 is integrally formed at the dashed line 48. However, it would also be conceivable for the rail 12 to be connected to the duct 20a of the housing cover 106 in some other way, for example by a high-pres~u,e hose.
In addition, the housing element 68 itself can be provided with fitting openings 44 for receiving the plunger cylinders 46 and a duct 20a, in such a way that the plunger cylinders 46 can be inserted directly into the housing element 68 with a press fit. Here too, the plunger cylinders 46 are configured in such a way that the delivery space 56 is connected to the duct 20a via the passage 62 and the annular duct 50. In this case, the rail 12 has only the openings 22 for receiving the injectors 24 but not the fitting openings 44 for the plunger cylinders 46.
The ples~e space 20 of the rail 12 can then be connected to the duct 20a of the housing element 68 either via high-plessule hoses or by virtue of the fact that the rail 12 is formed directly onto the housing element 68.
In the embodiment illustrated in Fig. 1, the housing element 68 is an integrated component of the cylinder head housing 14, and thus of the engine housing 92. Other embodiments in which other parts of the pump housing 66 are an integrated component of the engine housing 92, preferably of the cylinder head housing 14 of the intt?rn~l combustion engine 10, are however also conceivable. Here, for example the rail 12 can be formed onto the cylinder head housing 14 and also to the housing cover 106 or the housing element 68 so that these elements are integrated into the engine housing 92 or the cylinder head housing 14 via the rail 12. The housing cover 106 or side plate 80 can also be integrated into the engine housing 92 or the cylinder head housing 14 or combinations of these parts.
In order to ensure that the pres~ult; medium flows around the injectors 24 and the CA 022~1148 1998-10-19 plunger cylinders 46, possibilities other than the circumferential grooves 36 on the injectors 24 and the circumferential annular grooves which form part of the annular duct 50 may be provided on the plunger cylinders 46. It would be conceivable to have, for example, annular grooves on the inside of the openings 26 for the injectors 24 and/or in the fitting openings 44 for the plunger cylinders 46. It would also be possible for the injectors 24 to be connected to the rail 12 in some way other than by an ~tt~cl~ment element 40 and an abutment 42, for example via a shrink fit. Likewise, the plunger cylinders 46 may also be secured in the fitting openings 44 in some way other than by a press fit. For the method of operation it is in principle not of decisive importance whether the plunger cylinder 46 projects out of the component which receives the plunger cylinder 46, terrnin~tes flush with it or is covered and held by it. This applies likewise to the injectors 24 in the rail 12. In addition, the alignment of the axes 52 of the fitting openings 44 for the plunger cylinders 46 and of the opening axes 26 of the openings 22 for the injectors 24 does not necessarily have to be arranged parallel and in a plane. Other alignments are also conceivable.

Claims

1. A common-rail injection system for an internal combustion engine, comprising:
a rail having a pressure space and injector openings connected to said pressure space, wherein the rail also has a fitting opening;
fuel injectors received in said injector openings; and a plunger cylinder of a high pressure pump received in said fitting opening, said plunger cylinder having a delivery space receiving a fuel to be injected, and a passage communicating with said pressure space of said rail so that said high-pressure pump pumps the fuel from said delivery space to the pressure space of the rail via the passage.

2. The injection system as claimed in claim 1, wherein the injectors have inlet openings communicating with the pressure space of the rail.

3. The injection system as claimed in claim 1, wherein the injector openings of the rail have axes arranged parallel to one another and in a plane, so that the injectors lie parallel to one another and in the plane.

4. The injection system as claimed in claim 3, wherein the fitting opening for receiving the plunger cylinder has an axis extending parallel to, and in a plane with, the opening axes of the injector openings in the rail.

5. The injection system as claimed in claim 1, wherein the high-pressure pump has a pump housing, and the rail forms a part of the pump housing.

6. The injection system as claimed in claim 5, wherein the rail forms a housing cover of the pump housing.

7. The injection system as claimed in claim 5, wherein the rail is integrally formed onto the pump housing.

8. The injection system as claimed in claims 5, wherein the pump housing of the high-pressure pump, including the rail, form integrated components of a cylinder head housing of the internal combustion engine.

9. A common-rail injection system having a high-pressure pump which has a pump housing with housing cover, wherein the pump housing is an integrated component of a cylinder head housing of an internal combustion engine.