Note: Descriptions are shown in the official language in which they were submitted.
CA 022~1148 1998-10-19
9533-0004-3
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-
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
