Cylinder head for an internal combustion engine with fuel injection

In a cylinder head for a fuel injected internal combustion engine in which a nozzle holder with a fuel injection nozzle is mounted and engaged by a pressure tube disposed in a cylindrical recess, the pressure tube is axially forced into firm engagement with the nozzle holder by a hollow compression screw through which the pressure tube extends so that its free end projects outwardly and an injection pipe is mounted onto the free end of the pressure tube by means of a union nut for sealing the injection pipe to the pressure tube.

BACKGROUND OF THE INVENTION 
The invention relates to a cylinder head for an internal combustion engine 
with fuel injection wherein a fuel pipe is connected to a pressure tube 
for supplying fuel under pressure to an injection nozzle. 
Such a cylinder head is known from DE 31 28 523 C2 in which a thick-walled 
pressure tube is disposed in a cylindrical recess leading to the nozzle 
holder. The pressure tube is pressed onto a sealing seat on the nozzle 
holder by a compression nut, which surrounds an injection pipe originating 
from the injection pump and engages a flange structure firmly connected to 
the injection pipe. 
Upon removal of the injection pipe the high pressure seal on the nozzle 
holder is necessarily also loosened in this arrangement and this can lead 
to sealing problems on reassembly of the injection pipe. 
It is therefore the object of the invention to provide a conduit connection 
which is easy to assemble and which eliminates sealing problems at the 
high pressure seal connection between the pressure tube and the nozzle 
holder upon loosening and remounting of the injection pipe connection at 
the cylinder head. 
SUMMARY OF THE INVENTION 
In a cylinder head for a fuel injected internal combustion engine in which 
a nozzle holder with a fuel injection nozzle is mounted and engaged by a 
pressure tube disposed in a cylindrical recess, the pressure tube is 
axially forced into firm engagement with the nozzle holder by a hollow 
compression screw through which the pressure tube extends so that its free 
end projects outwardly and an injection pipe is mounted onto the free end 
of the pressure tube by means of a union nut for sealing the injection 
pipe to the pressure tube. 
Assembly and dismantling of the injection pipe and pressure tube are 
simplified by the special arrangement and configuration of the high 
pressure pipe connection because the pressure tube remains firmly mounted 
in the cylinder head when the fuel pipe is disconnected. A further 
advantage lies in the fact that reliable sealing at the nozzle holder 
continues to be ensured independent of the dismantling of the injection 
pipe. In addition, the design according to the invention permits 
leak-testing on the pre-assembled cylinder head.

DESCRIPTION OF A PREFERRED EMBODIMENT 
A nozzle holder 2 with a fuel injection nozzle 3 is mounted in the cylinder 
head 1 of an air-compressing fuel-injected internal combustion engine. A 
fixed-position, thick-walled pressure tube 5 is also disposed in a 
cylindrical recess 4 in the cylinder head 1, which recess 4 has a stepped 
configuration and extends transversely to the nozzle holder 2. The 
thick-walled pressure tube 5 extends over the full length of the 
cylindrical recess 4 with a radial distance from the wall 6. The free end 
of the pressure tube 5 protrudes from the cylinder head 1 and forms a 
connector for an injection pipe 7 connected to an injection pump (not 
shown). 
The pressure tube 5 is provided with an external collar 8 which has a 
conical or spherical contact surface 9 at the injection pipe end for 
engagement by a hollow compression screw 10 screwed into the cylindrical 
recess 4. The compression screw 10 has, in turn, a conical seating surface 
11 corresponding to the contact surface 9 of the pressure tube 5. The 
conical end surface 12 at the nozzle holder end of the pressure tube 5 is 
firmly seated by the force of the compression screw 10 so that it seals 
against a correspondingly configured sealing seat 13 formed at the 
connection of the nozzle holder 2. The position of the pressure tube 5 is 
therefore fixed in the cylindrical recess 4 of the cylinder head 1. 
The pressure tube 5 protrudes beyond the compression screw 10 and is 
provided at its outer end with an external thread 14 for a union nut 15 by 
means of which the injection pipe 7 is sealingly connected to the pressure 
tube 5. The injection pipe 7 has an enlarged end with a conical end 
surface 16 which is sealingly engaged by the force of the union nut 15 
with a matching seating surface 17 of the pressure tube 5. 
The pressure tube 5 has an internal passage 18 which comprises two passage 
sections, 18a, 18b, of which the passage section 18b at the injection pipe 
end has a larger diameter and is adapted to accommodate a fuel filter 19. 
Adjacent the collar 8 there is a sealing ring 21 disposed in a groove 20, 
the sealing ring 21 being sized so as to close and seal the annular 
intermediate space 22 between the pressure tube and the wall of the recess 
4. A leakage fuel or fuel return passage 24 provides for communication 
between the annular intermediate space 22 which is in communication with a 
fuel leakage passage in the nozzle holder and a collecting passage 23 in 
the cylinder head 1. 
FIG. 2 shows a leakage fuel path in the nozzle holder 2 which includes a 
central passage 25 originating from the fuel injection nozzle 3, a radial 
passage 26 leading outwardly from the central passage 25 and an annular 
passage 27, which is in communication with the annular intermediate space 
22. The conical end surfaces, seating surfaces and sealing surfaces at the 
nozzle holder and/or injection pipe ends can also, if appropriate, have a 
spherical configuration. 
In addition, an angular position locking arrangement can be provided to 
prevent rotation of the pressure tube 5 during the assembly of the 
injection pipe 7. It consists of a radial lug on the pressure tube 5, for 
example, at the collar 8, and a correspondingly matched groove 29 in the 
cylindrical recess or of a cylindrical pin in the cylinder head and a flat 
or axial groove machined into the pressure tube.