Injection valve

An injection nozzle for fuel injection systems of internal combustion engines, the nozzle being arranged to inject fuel into the intake tube of the engine. The injection valve includes a valve housing of ferromagnetic material, in which a tubular connection element which functions as a core with which an armature is arranged to cooperate. Joined to the valve housing is a nozzle body having a valve seat with which a sealing section of a nozzle needle also arranged to cooperate. The nozzle needle is guided by guide sections in a guide bore of the nozzle body, and the guide section adjacent to the sealing section is provided with metering bores. By metering fuel upstream of the valve seat, the fuel metering operation is prevented from being impaired by deposits.

BACKGROUND OF THE INVENTION 
The invention is based on an injection valve as generally defined 
hereinafter. An injection valve is already known in which to avoid 
deposits at the metering cross sections, which are the result of 
combustion residues in the intake tube or residues from fuel evaporation 
and all oil which can cause a change in the metered fuel quantity, the 
metering cross sections are shifted to upstream of the sealing section and 
embodied as surfaces at a guide section of the nozzle needle. The 
disadvantage here is that when the metering cross sections are 
manufactured, the manufacturing tolerances of both the guide bore and the 
metering faces at the guide section must be taken into account. 
OBJECT AND SUMMARY OF THE INVENTION 
The injection valve according to the invention and having the 
characteristics revealed later herein has the advantage over the prior art 
that the formation of deposits in the area of the fuel metering location 
is avoided, and this nozzle design which incorporates the fuel metering 
locations as taught herein are easy to manufacture. 
A particularly advantageous feature of the invention is the embodiment of 
the metering bores at an inclination to the guide bore, as a result of 
which the ejected fuel spray can be acted upon in terms of its shape and 
preparation, in particular by generating a swirl motion thereto. 
The invention will be better understood and further objects and advantages 
thereof will become more apparent from the ensuing detailed description of 
preferred embodiments taken in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The fuel injection valve shown in FIG. 1 for a fuel injection system of a 
mixture-compressing internal combustion engine having externally supplied 
ignition has a valve housing 1 of ferromagnetic material, in which a 
magnetic coil 3 is disposed on a coil carrier 2. The magnetic coil 3 is 
supplied with electric current via a plug connection 4, which is embedded 
in a plastic ring 5 that partially surrounds the valve housing 1. 
The coil carrier 2 of the magnetic coil 3 is seated in a coil chamber 6 of 
the valve housing 1 on a connection pipe 7 carrying the fuel, for instance 
gasoline, and the connection pipe 7 protrudes partway into the valve 
housing 1. Remote from the fuel pipe 7, the valve housing 1 partially 
surrounds a nozzle body 9. 
The cylindrical armature 14 of the fuel injection valve is located between 
an end face 11 of the connection pipe 7 and a stop plate 12, which has a 
predetermined thickness for the purpose of precisely adjusting the valve 
and which is mounted upon an internal shoulder 13 of the valve housing 1. 
The armature 14 is made of corrosion-resistant magnetic material. A 
compression spring 16 acting upon the armature 14 is disposed between the 
armature 14 and a tube insert 15, the latter being secured in the 
connection pipe 7 by constricting the pipe 7. On the other end, a nozzle 
needle 17 is secured in the armature 14, being inserted into an armature 
bore 19 of the armature 14 with an annularly grooved end 18 and is 
retained therein by the armature material being pressed radially inward 
into the annular grooves of the annularly grooved end 18. 
With radial play, the nozzle needle 17 penetrates through opening 20 in the 
stop plate 12 and a guide bore 21 in the nozzle body 9 and with the lower 
extremity of the needle 22 arranged to emerge from an injection opening 23 
of the nozzle body 9. A conical valve seat face 24 which cooperates with a 
conical sealing section 25 on the nozzle needle 17 is formed between the 
guide bore 21 of the nozzle body 9 and the injection opening 23. The 
length of the nozzle needle 17 and of the armature 14 is dimensioned, 
beginning at the sealing section 25, such that in the nonexcited state of 
the magnetic coil 3 the armature 14 leaves a working gap A open with 
respect to the end face 11 of the tubular connection element 7. 
The nozzle needle 17 has two guide sections 33 and 34, which guide the 
nozzle needle 17 in the guide bore 21 and also have an axial passageway 
for the fuel, to which end the guide section 33 located upstream of the 
guide section 34 is embodied as a rectangle, for instance. 
Between the guide opening 20 and the circumference of the stop plate 12, a 
recess 37 is provided, the inside diameter of which recess is greater than 
the diameter of the nozzle needle in the corresponding region 38 of the 
nozzle needle 17, that is, it is greater diameter between the annularly 
grooved end 18 and the stop shoulder 39 of the nozzle needle 17. In the 
excited state of the magnetic coil 3, the armature 14 is moved in the 
opening direction of the nozzle needle 17 counter to the force of the 
compression spring 16 and rests with the stop shoulder 39 on the stop 
plate 12. 
The magnetic flux is conducted through the jacket of the valve housing 1 
via a magnetic flux conductor step 40 to the cylindrical armature 14 and 
from there back to the valve housing via the tubular connection element 7, 
which acts as a core and has a conductive flange 41. The magnetic flux 
conductor step 40 of the valve housing 1 points radially inward and 
surrounds the armature 14. 
In accordance with the invention, metering bores 43, for instance four 
possibly in number, are cut into the cylindrically embodied guide section 
34 adjacent to the sealing section 25 on the nozzle needle 17. By way of 
these bores 43, fuel can flow from upstream of the guide section 34 to 
downstream thereof whereupon a pressure drop of approximately 80 to 85% 
takes place, while the remaining pressure, which serves the purpose of 
fuel preparation, decreases between the injection opening 23 and the 
extremity of needle 22. The metering bores 43 are not opened in the radial 
direction with respect to the guide bore 21 and can extend either parallel 
to the guide bore 21 or, as shown in FIG. 2, inclined with respect 
thereto; these metering bores can additionally extend in such manner that 
the fuel which emerges from the metering bores 43 can be provided with a 
swirl or spin motion. 
The metering bores 43 can be manufactured in a simple manner, unaffected by 
the manufacturing tolerances of the guide bore 21 and the guide section 
34. By disposing the metering bores 43 upstream of the valve seat face 24, 
deposits in the metering bores 43 are avoided. Deposits in the relatively 
wide gap between the extremity of neddle 22 and the wall of the injection 
opening 23 have only a negligible effect on the metered fuel quantity. 
The foregoing relates to a preferred exemplary embodiment of the invention, 
it being understood that other variants and embodiments thereof are 
possible within the spirit and scope of the invention, the latter being 
defined by the appended claims.