Fuel injection system

A fuel injection system for dosing and atomizing fuel under high pressure into the cylinders of an internal combustion engine has a continuously operating, controllable-flow-rate fuel pump and at least one adjusting drive associated with injection nozzles respectively for each cylinder of the engine. The flow rate of the fuel pump is controlled by the sum of the fuel quantities to be fed per unit time to all of the injection nozzles for controlling the fuel dose injected into each cylinder. The adjusting drive at least opens a fuel path to the injection nozzle for each cylinder at the correct time to control the injection timing. Separating the dose and timing controls in this way simplifies the structure required for both controls.

BACKGROUND OF THE INVENTION 
The invention relates to a fuel injection system for dosing and atomizing 
fuel under high pressure into an internal-combustion engine. 
A fuel injection system has the functions, for each cylinder of an 
internal-combustion engine, to dose precisely the quantity of fuel 
supplied as a function of an operating state, to introduce the fuel into 
the combustion air at the correct time and to atomize the fuel 
sufficiently finely via the pressure gradient prevailing at an injection 
nozzle. 
Such a fuel injection system is applicable to both diesel and Otto engines, 
to both single-cylinder and multiple-cylinder engines, and to both direct 
injection into the cylinder and suction pipe injection. The fuel injection 
system according to the invention is however intended preferably for 
diesel engines with direct injection under high pressure into each 
individual engine cylinder. 
Numerous fuel injection systems are known. In the majority of known 
injection systems, a mechanically or hydraulically driven piston pump 
doses the fuel into the combustion air intermittently at a controllable 
ties pressurises it, and displaces it through the injection nozzle. The 
quantity of fuel injected in this case is varied by varying the delivery 
stroke of the piston of the piston pump (so-called stroke regulation), by 
varying the quantity of fuel in the pump chamber of the piston pump 
(so-called charge regulation), or by varying the throttle cross-sections 
effective during the delivery (so-called throttle regulation). 
It is also known to provide a separate pump piston for each cylinder of the 
internal-combustion engine in a series of pumps or pump/injection nozzle 
combinations. Distributor pumps are also known, wherein a plurality of 
cylinders of the internal-combustion engine are alternatively supplied 
from one pump piston in the pump. 
These known injection systems have a number of disadvantages. They require 
one or more intermittently driven pump pistons. The structural outlay for 
the pump piston drive is high due to the intermittent loading. 
Furthermore, the fuel pump must controllably time the delivery for 
variable speed operation. The structural outlay for this purpose is 
substantial. 
Lastly, a fuel injection system is also known wherein a non-periodic fuel 
pump delivers fuel at regulated pressures into a system common to all the 
cylinders of the internal-combustion engine. The injection quantity is 
regulated by the fuel pressure and the time cross-section of the injection 
nozzle at each cylinder--i.e., the integral of the free flow cross-section 
of injection orifice over the time. It is therefore necessary to control 
precisely the time cross-section of each injection nozzle. This is 
performed either mechanically or electromagnetically. 
Even the last-mentioned injection system has serious disadvantages. In 
order for the fuel pump to be able to deliver at regulated pressure, it 
must deliver more fuel than is required for the injection, and the control 
of the time cross-section of the injection nozzles necessitates a 
considerable structural outlay. Control of the injection quantity by means 
of the time cross-section becomes increasingly difficult, or even 
impossible, as the injection time becomes shorter. 
SUMMARY OF THE INVENTION 
The underlying aim of the invention is to obviate the described 
disadvantages of the conventional injection systems. Particularly, it is 
proposed to develop a fuel injection system which requires a small 
structural outlay for drive and control means, operates reliably, and is 
particularly suitable for high pressures and short injection times. 
This aim is achieved in a fuel injection system for dosing and atomizing 
fuel into an internal-combustion engine according to the invention by at 
least one injection nozzle for each cylinder of the internal-combustion 
engine, a continuously operating fuel pump with infinitely controllable 
flow rate controlled by the sum of the injection quantities to be fed per 
unit time to all the injection nozzles of the internal-combustion engine 
(so that the dosing of the injection quantities is controlled by means of 
the fuel pump), a fuel path forming a collective pressure chamber, 
preferably discretely into which the entire fuel flow from the fuel pump 
is introduced and to which every injection nozzle is connected, and at 
least one adjusting drive associated with each injection nozzle for 
opening the injection orifice of the latter at the correct time or phase. 
The end of the injection may also be controlled by the adjusting drive. 
However, on the one hand, the adjusting drive need only control the start 
of injection, and optionally the end of injection, but not the time 
cross-section of the injection, because the dosing of the injection 
quantity is not controlled by the opening to closing time cross-section of 
the injection nozzle. On the other hand, only the flow rate is regulated 
the fuel pump, and not the timing and duration of the injection. 
Numerous advantages are attained by the construction of the fuel injection 
system according to the invention. Only one central fuel pump is necessary 
for delivering the fuel to be fed to the cylinders per unit of time. This 
fuel pump delivers continuously without pressure surges and therefore with 
a nonpulsatory driving torque. Its drive is therefore simple and excites 
no mechanical or acoustical vibrations. Moreover its drive need not occur 
in correct phase, and because the fuel pump delivers only the total 
quantity of fuel required per unit of time, its driving power requirement 
is minimalized. 
The entire dosing of the injection quantity is controlled by adjusting the 
flow rate of the fuel pump. No other adjustments need be effected at the 
fuel pump. The flow rate regulation of the fuel pump requires only a small 
mechanical outlay, for example the fuel pump may be driven by the 
internal-combustion engine proportionally to the speed of the latter. 
The timing of the injection is controlled by the adjusting drive, which 
merely has to control the start of the injection at the correct time and 
can therefore be constructed as a simple two-position-adjusting drive. If 
the injection is not in any case terminated before the end of the 
modulation of the adjusting drive, then the adjusting drive also 
determines the end of the injection and hence the injection period. 
Conjointly with the element which is actuates, the adjusting drive merely 
constitutes a switch. 
Because the entire regulation of the fuel injection system according to the 
invention is the flow rate regulation of the fuel pump and the timing 
regulation of the adjusting drive, which is simply a 
two-position-adjusting drive, the mechanical outlay for regulating the 
fuel injection system according to the invention is extremely small. The 
modulation of the adjusting drive and the flow rate regulation are 
preferably effected by means of electrical signals or impulses which are 
supplied by electrical or electronic control devices which permit a 
plurality of parameters of influence, e.g., speed of the 
internal-combustion engine, load or accelerator position, state of the 
intake air, and cooling water temperature of the internal-combustion 
engine, etc., to be processed centrally and converted into appropriate 
control or adjustment quantities. 
As an advantageous further development of the invention it may be provided 
that a flow throttle is constructed in nozzle pipes downstream of the 
collective pressure chamber, and downstream of the flow throttle a nozzle 
accumulator from which the fuel passes to the injection orifice during the 
injection. In the nozzle accumulator the fuel pressure falls rapidly 
during the injection below the pressure in the collective pressure 
chamber, and in the interval between two injections the pressure in the 
pressure accumulator increases slowly again. The injection starts with the 
modulation of the adjusting drive and terminates not later than when the 
adjusting drive reverts to its initial state. But the injection may end 
even beforehand if the injection nozzle closes spontaneously due to the 
pressure drop in the nozzle accumulator when the closing pressure of the 
injection nozzle is attained. Due to this it becomes possible to achieve 
shorter injection periods than those which result from the time interval 
between the start and end of the modulation of the adjusting drive. 
Extremely short injection periods become possible in this way. 
As an advantageous further development of the above-described development, 
it may further be provided that, in parallel with the first arrangement 
comprising flow throttle and nozzle accumulator, in one or more bypass 
pipes, a second flow throttle, a second nozzle accumulator downstream of 
the second flow throttle and a way-valve are connected to the nozzle pipe, 
whilst the way through the bypass pipe to the injection orifice can be 
open at a different time from the way through the first arrangement. In 
this way the injection curve cn be influenced within wide limits in that 
the two or more nozzle accumulators which are associated with each 
injection nozzle, and which preferably have different size, are connected 
displaced in phase to the injection nozzle. 
In the fuel injection system according to the invention it is preferred to 
use injection nozzles which exhibit a nozzle chamber from which the 
injection nozzle starts and which constitutes one end of the nozzle pipe, 
a displaceable nozzle needle extending through the nozzle chamber, which 
can open and close the injection orifice, and a nozzle spring which loads 
the nozzle needle in the closing direction and permits a displacement of 
the nozzle needle in the opening direction when the fuel pressure in the 
nozzle chamber exceeds a specific value. If such an injection nozzle is 
preceded by a way-valve in the nozzle pipe actuated by the adjusting 
drive, then the way-valve must be dimensioned so that it withstands the 
fuel pressures occurring and allows the total injection quantity to pass 
in the open state. In the case of the fuel pressures necessary for diesel 
engines and short injection periods, this necessitates comparatively 
large-dimensioned way-valves with comparatively large moving masses, which 
in turn necessitate comparatively high adjusting forces and thus a 
powerful adjusting drive. 
As an advantageous development of the invention, therefore, in conjunction 
with the above-described injection nozzle, a hydraulically actuated 
shut-off valve in the nozzle pipe upstream of the nozzle chamber and a 
preliminary control valve actuated by the adjusting drive in a pipe 
branching from the nozzle pipe may be provided, whilst the modulated 
adjusting drive opens the preliminary control valve and thereby loads the 
shut-off valve with the fuel pressure in the opening direction. Because 
with this construction the adjusting drive need only actuate the 
preliminary control valve and the injection quantity does not flow through 
the preliminary control valve, so that its free flow cross-section can be 
small, the adjusting drive need exert only comparatively small adjusting 
forces, by which is comparatively small mass is moved for a short 
distance. 
As an advantageous development of the invention it may be provided that the 
fuel pump is a piston pump of infinitely controllable delivery stroke of 
multiple radial construction or multiple axial construction. The fuel pump 
is preferably driven by the internal-combustion engine proportionally to 
the speed of the latter and it is provided with an adjusting member by 
means of which the delivery stroke of the fuel pump can be influenced, 
whilst the control quantity attacking the adjusting member is a function 
at least of the accelerator position of the internal-combustion engine. In 
order to keep the mechanical outlay for the actuation of the adjusting 
member of the fuel pump small, the adjusting forces required for the 
purpose should be as small as possible. It may therefore be provided as an 
advantageous embodiment of the invention that the fuel pump exhibits an 
adjusting piston slidable in the pump housing, by the position of which 
the delivery stroke of the fuel pump is determined and which is loaded 
with fuel pressures, and that the adjusting member is a sliding control 
slide valve which is arranged in the delivery stream in the pressure pipe 
of the fuel pump and at which the fuel pressure forces cancel each other, 
whilst the control slide valve adjusts the fuel pressures loading the 
adjusting piston by means of at least one variable throttle cross-section. 
Because the fuel pressures generated by the fuel pump itself are utilized 
to load the adjusting piston of the fuel pump, and the control slide valve 
is relieved of pressure, only very small adjusting forces need be exerted 
on the control slide valve and hence in order to adjust the flow rate of 
the fuel pump. The flow rate regulation occurs as a function of the speed 
of the internal-combustion engine and of its accelerator position and also 
optionally of other parameters of influence such as ambient temperature, 
ambient pressure, cooling medium temperature etc., by means of an 
electrical or electronic control device which delivers an electrical 
control signal on the basis of which an electromechanical adjusting drive 
actuates the control slide valve. 
Further advantageous developments of the invention will emerge from the 
patent claims and from the following description of exemplary embodiments 
of the invention making reference to the drawings, wherein:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The injection system illustrated schematically in its simplest embodiment 
in FIG. 1 comprises a fuel pump 2 which delivers fuel from a fuel tank 4 
under pressure into a pressure pipe 6. The fuel pump 2 is a continuously 
delivering fuel pump which is constructed e.g., as an axial pump or radial 
pump with a plurality of pump cylinders and pump pistons. The fuel pump 2 
is driven at its driving shaft 8 by the internal-combustion engine, not 
shown, to which the fuel injection system belongs, at a speed proportional 
to the speed of the internal-combustion engine. The flow rate Q delivered 
by the fuel pump 2, i.e., the volume of fuel delivered by the fuel pump 
per unit of time, is infinitely controllable at the fuel pump. The control 
is effected by means of a control quantity signal F given to an adjusting 
member of the fuel pump 2, not shown in FIG. 1, which in the exemplary 
embodiment according to FIG. 1 is equal to a position signal H derived 
from the position of a drive lever or accelerator pedal 10. The flow rate 
Q is thus proportional to the speed of the internal-combustion engine and 
to the position signal H and is adjusted so that it is equal to the sum of 
all of the injection quantities to be fed per unit of time. The total flow 
rate Q passes through the pressure pipe 6 into a collective pressure 
chamber 12. From the collective pressure chamber 12 a particular nozzle 
pipe 14 leads to each of the cylinders, not shown in FIG. 1, of the 
internal-combustion engine, and issues into an injection nozzle 16 
schematically illustrated in FIG. 1, which is shown for only one of the 
cylinders in FIG. 1. The injection nozzle 16 is maintained closed by a 
nozzle spring 18 and opened when the pressure of the fuel in the nozzle 
pipe 14 applied to the injection nozzle 16 exceeds a specific value. 
Upstream of the injection nozzle 16 a way-valve 20 is arranged in the 
nozzle pipe 14. Such a way-valve 20 is provided in each of the nozzle 
pipes 14, but illustrated only once in FIG. 1. In the exemplary embodiment 
illustrated the way-valve 20 is constructed as a 3/2 way-valve and 
maintains the nozzle pipe 14 open in its position A, whereas in its 
position B it blocks the nozzle pipe 14 and connects the injection nozzle 
16 to a pressureless outlet 22. The way-valve 20 may also be constructed 
as a 2/2 way-valve which then, in its blocking position, merely blocks the 
nozzle pipe 14 without establishing a connection between the injection 
nozzle 16 and an outlet. Each of the way-valves 20 is actuated by an 
adjusting drive 24. The term adjusting drive is used for a drive means 
that delivers the force required to actuate a control element connected to 
the drive means. The adjusting drive 24 is shown only schematically in 
FIG. 1 and is preferably constructed as an electromagnet with a sliding 
armature. The adjusting drive 24 itself is modulated (i.e. activated) by a 
current impulse I generated in correct phase by means of a control device 
not shown, and maintains the way-valve 20 in its position A during the 
period of the current impulse I. 
In service the fuel pump 2 delivers continuously the flow rate Q which is 
proportional to the speed of the internal-combustion engine and is 
infinitely adjusted in conformity with the operating conditions by means 
of the control quantity signal F. For each cylinder of the 
internal-combustion engine the control device supplies the current impulse 
I in correct phase for a specific period. The adjusting drive 24 maintains 
the way-valve 20 in its position A for the period of the current impulse 
I, so that fuel can flow out during the open period of the injection 
nozzle 16 determined by the impulse period. The pressure in the collective 
pressure chamber 12 is then automatically adjusted so that the total flow 
rate Q is discharged during the open periods of the injection nozzles 16. 
A second embodiment of the injection system according to the invention is 
explained hereinbelow with reference to FIG. 2. Parts and elements which 
are identical to parts and elements of the first embodiment according to 
FIG. 1 are designated by the same reference numerals in FIG. 2 and will 
not be explained afresh. Differing from the embodiment according to FIG. 
1, in the embodiment according to FIG. 2 there is constructed in each 
nozzle pipe 14, downstream of the collective pressure chamber 12 a flow 
throttle 26, and downstream of the flow throttle 26 an accumulator chamber 
which is designated the nozzle accumulator 28 because it is associated 
with an injection nozzle in each case. 
So long as the adjusting drive 24 associated with an injection nozzle 16 is 
not modulated by a current impulse I, the way-valve 20 is closed and 
pressure builds up gradually in the associated nozzle accumulator 28. Then 
when the way-valve 20 is opened and consequently the associated injection 
nozzle 16 opens, the fuel flows away from the nozzle accumulator 28 
through the injection nozzle, whilst the pressure in the nozzle 
accumulator 28 decays rapidly due to the preceding flow throttle 26. This 
has the result that the pressure in the nozzle pipe 14 upstream of the 
injection nozzle 16 falls below the closing pressure of the injection 
nozzle 16, so that the latter closes and the injection ends before the 
adjusting drive 24 brings the way-valve 20 into its closed position. In 
this manner short injection periods are obtained which are shorter than 
the period of the current impulse I. 
FIG. 2 also shows schematically the control devices to generate the current 
impulses I and the control quantity signal F. A signal transducer 30 picks 
up from the crankshaft or the camshaft 29 of the internal-combustion 
engine impulses in correct phase, the frequency of which is proportional 
to the speed of the internal-combustion engine, and supplies a phase 
signal Ph. The phase signal Ph is passed on the one hand to a signal 
converter 32, which generates a speed signal n.sub.M, and on the other 
hand to an electronic control device 34 which is also fed with the speed 
signal n.sub.M and further signals which are a function of the operating 
state of the internal-combustion engine and of the ambient conditions, 
e.g., an ambient pressure signal p.sub.A and an ambient temperature signal 
T.sub.A. The control device 34 supplies for each cylinder of the 
internal-combustion engine engine-synchronous current impulses I regulated 
in their phase position and duration, which are amplified by a power 
amplifier 36 and fed by the latter to the adjusting drive 24, constructed 
as electromagnets, associated with the individual injection nozzles 16. 
The speed signal n.sub.M is also passed to a second control device 38 which 
is fed additionally with the position signal H derived from the position 
of the drive lever 10 and with the ambient pressure signal p.sub.A and the 
ambient temperature signal T.sub.A and generates the control quantity 
signal F which is passed to an electromechanical adjusting device 40 which 
actuates the adjusting member, not shown, of the fuel pump 2 in order to 
adjust its flow rate. The control quantity signal F is also passed to the 
control device 34 and participates in the generation of current impulses 
I. 
It is clear that in the fuel injection system according to the invention 
the only control and regulation processes which have to be performed 
mechanically are the adjustment of the flow rate of the fuel pump 2 and 
the opening in correct phase of the injection nozzles. 
FIG. 3 shows schematically and as a detail a third embodiment of the 
invention, in which once again the same reference numerals are used for 
parts and elements already explained and said parts and elements are not 
explained afresh. 
A bypass pipe 42 is connected in parallel with the nozzle pipe 14. The 
bypass pipe 42 contains a second flow throttle 44, arranged downstream of 
the latter a second nozzle accumulator 46, and downstream of the latter a 
second way-valve 48 which is maintained in its open position by a second 
adjusting drive 50, whilst the second adjusting drive 50 is modulated by a 
current impulse I.sub.2. The fuel injection system according to FIG. 3 
thus exhibits a second arrangement of flow throttle 44 and nozzle 
accumulator 46 in parallel with the first arrangement of flow throttle 26 
and nozzle accumulator 28, so that it is possible to influence the 
injection curve by different dimensioning of the nozzle accumulators 28 
and 46 and by different phase positions and periods of the current 
impulses I.sub.1 and I.sub.2 by which the adjusting drives 24 and 50 
constructed as electromagnets are modulated. This possibility can be 
utilized, e.g., for the preinjection or fuel. 
As may be seen in FIG. 3, in the exemplary embodiment illustrated the 
way-valves 20 and 48 are constructed as 2/2 way-valves. 
FIG. 3 also shows more accurately the construction of the injection nozzle 
16, which exhibits a nozzle needle 54 slidable in an injection nozzle 
housing 52 and projecting into a nozzle chamber 56 which constitutes the 
end of the nozzle pipe 14 and from where the injection orifice 58 starts. 
The nozzle needle 54 is acted on by the nozzle spring 18 which presses 
against the nozzle needle in the closing direction so that the nozzle 
needle maintains the injection orifice 58 closed until the pressure in the 
nozzle chamber 56 exceeds a specific value. 
FIG. 4 shows a variant of the injection system illustrated in FIG. 3. The 
injection system illustrated in FIG. 4 differs from the injection system 
according to FIG. 3 substantially in the construction of the injection 
nozzle 16, the arrangement of the adjusting drive 24 and the absence of a 
way-valve in the nozzle pipe 14. 
The nozzle spring 18 of the injection nozzle 16, which has the same 
construction as the injection nozzle 16 according to FIG. 3, is 
pretensioned so that the nozzle needle 54 maintains the injection orifice 
58 closed even at the maximum fuel pressure occurring in the nozzle 
chamber 56. The injection orifice 58 is however opened when an additional 
force acts upon the nozzle needle 54 in the opening direction. Said force 
is exerted by the adjusting drive 24 during the period of the current 
impulse I.sub.1. The adjusting drive 24 is constructed as an electromagnet 
which exhibits, in a magnet housing 59, a solenoid 62 and a moving 
armature 60. The moving armature 60 is connected firmly to the nozzle 
needle 54 which extends through the housing 59 and is loaded at its top 
end in FIG. 4 by the nozzle spring 18. 
When the adjusting drive 24 is loaded by the current impulse I.sub.1, the 
nozzle needle 54 opens the injection orifice 58 so that the fuel stored in 
the nozzle accumulator 28 is discharged through the injection nozzle, 
whilst initially the bypass pipe 42 is still maintained closed by means of 
the second way-valve 48. Then, with a certain phase displacement with 
reference to the current impulse I.sub.1, the second adjusting drive 50 is 
loaded with the current impulse I.sub.2, so that the second way-valve 48 
opens and the fuel is injected out of the second nozzle accumulator 46. 
The combination of the injection nozzle 16 and the adjusting drive 24 
illustrated in FIG. 4 may also be provided in the case of the embodiments 
according to FIGS. 1 and 2 instead of the combination of injection nozzle, 
way-valve and adjusting drive provided there. 
FIG. 5 shows a further variant of the exemplary embodiment of the injection 
system illustrated in FIG. 3. The variant illustrated in FIG. 5 differs 
from the injection system according to FIG. 3 in that the second way-valve 
48 is combined with the injection nozzle 16 and the injection nozzle 
itself constitutes the adjusting drive for the second way-valve 48. 
In the injection system according to FIG. 5 the nozzle spring 18 is 
pretensioned so that the nozzle needle 54 opens the injection orifice 58 
when the pressure of the fuel in the nozzle chamber 56 exceeds a specific 
value. The top end in FIG. 5 of the nozzle needle 54 is constructed as a 
valve element with an annular groove 64 which can open and close the 
communication between an inlet 66 and an outlet 68 which are constructed 
in the injection nozzle housing 52 and located in the bypass pipe 42. The 
section of the bypass pipe 42 arranged downstream of the outlet issues 
into the nozzle chamber 56. The communication between the inlet 66 and the 
outlet 68 is opened when the nozzle needle 54 has executed a specific 
stroke. 
In service the nozzle pipe 14 is initially opened by the current impulse 
I.sub.1, so that the nozzle needle 54 opens the injection orifice 58 and 
the injection commences with fuel from the first nozzle accumulator 28. 
During its upward stroke the nozzle needle 54 opens the second way-valve 
48, i.e., the communication between the inlet 66 and the outlet 68, so 
that the fuel from the second nozzle accumulator 46 is then also injected. 
Although the nozzle needle 54 constitutes the adjusting drive of the 
second way-valve 48, this produces no additional forces upon the nozzle 
needle. 
FIG. 6 shows a further variant of the embodiment illustrated in FIG. 3. In 
the injection system according to FIG. 6 the two way-valve 20 and 48 are 
combined structurally into a unit so that they are actuated in common by 
the sole adjusting drive 24. 
The injection nozzle 16 opens when the pressure of the fuel in the nozzle 
chamber 56 exceeds a specific value. 
The unit constituted by the two way-valves comprises a housing 70 and a 
valve slide 72 which can open and close the communication between the 
inlet 66 and the outlet 68 of the first way valve 48 and also establishes 
a communication between the outlet 68 and an outlet 74 when the 
communication between the inlet 66 and the outlet 68 is blocked. The valve 
slide 72 can also open and close a communication between an inlet 76 and 
an outlet 78 which are constructed in the housing 70 and associated with 
the first way-valve 20, and can also establish a communication between the 
outlet 78 and the outlet 22 of the first way-valve 20 when the 
communication between the inlet 76 and the outlet 78 is blocked. 
The valve slide 72 is maintained in its closed position, illustrated in 
FIG. 6, by a valve spring 80. When the adjusting drive 24 is loaded by the 
current impulse I, the valve slide 72 initially opens both outlets 22 and 
74 simultaneously. Whilst the valve stroke s is increasing--i.e., the 
valve slide 72 moves further upwards in FIG. 6--the valve slide 72 first 
opens the communication between the inlet 76 and the outlet 78 of the 
first way-valve 20, whereafter it opens the communication between the 
inlet 66 and the outlet 68 of the second way-valve 48, so that the 
injection occurs initially from the first nozzle accumulator 28 and then 
also from the second nozzle accumulator 46. 
The force of the adjusting device 24 is transmitted to the valve slide 72 
in that the armature 60 of the adjusting drive constructed as an 
electromagnet is firmly connected to the valve slide 72. 
In the control diagram illustrated in FIG. 6a the various free valve 
crosssections A are shown as a function of the valve stroke s for the 
embodiments according to FIG. 6. 
FIG. 7 shows in greater detail a first exemplary embodiment of a 
combination of injection nozzle 16, way-valve 20 and adjusting drive 24, 
as it is applicable to the embodiments according to FIGS. 1 and 2 of the 
injection system. With appropriate variation, the combination according to 
FIG. 7 may also be applied to the embodiment according to FIG. 3, the 
variation consisting solely in the fact of providing a connection for the 
bypass pipe 42 downstream of the way-valve 20 in FIG. 7. 
Here, as in all the other Figures, the same reference numerals are used for 
parts and elements in FIG. 7 which are identical to parts and elements of 
the exemplary embodiments previously described. 
The adjusting drive 24 is constructed as an electromagnet with a solenoid 
62 in a magnet housing 59 and with a moving armature 60. The valve slide 
72 of the way-valve 20 constructed as a 3/2 way-valve is firmly connected 
to the armature 60. The valve slide 72 is slidable in the housing 70 and, 
in its position illustrated in FIG. 7, connects the outlet 22 to the 
outlet 78, to which the nozzle chamber 56 of the injection nozzle 16 is 
connected. When, the adjusting drive 24 being modulated by the current 
impulse I, the valve slide 72 is slid out of its position illustrated 
counter to the force of the valve spring 80 towards the right-hand side of 
FIG. 7, it connects the inlet 76 to the outlet 78, so that the nozzle 
chamber 56 is then pressure loaded and the nozzle needle 54 is displaced 
counter to the pretensioning force of the nozzle spring 18 and opens the 
injection orifice 58. 
FIG. 8 shows a second exemplary embodiment of the combination of injection 
nozzle 16 and adjusting drive 24, which is suitable for the injection 
system according to FIG. 2. In the combination illustrated in FIG. 8, the 
flow throttle 26, the nozzle accumulator 28 and the adjusting drive 24 are 
structurally integrated in the injection nozzle housing 52. In a recess at 
the top end (in FIG. 8) of the injection nozzle housing 52 there is fitted 
an insert 82 in which the flow throttle 26 is constructed. Downstream of 
the insert 82, coaxially thereto in the injection nozzle housing 52, there 
is constructed the nozzle accumulator 28, from which a plurality of 
channels 84 lead through the injection nozzle housing to the nozzle 
chamber 56. Between the nozzle accumulator 28 and the nozzle chamber 56 
the injection nozzle housing contains a further chamber in which the 
adjusting drive 24 is arranged coaxially, being constructed in an 
electromagnet, and attacks the nozzle needle 54 directly by its armature 
60. The nozzle spring 18 arranged in a further recess of the injection 
nozzle housing, above the adjusting drive 24 in FIG. 8, maintains the 
nozzle needle 54 in its closed position counter to the maximum fuel 
pressure occurring. The nozzle needle 54 is slid in the opening direction 
only when the current impulse I modulates the adjusting drive 24. 
As may be seen in FIG. 8, the injection nozzle may also be constructed as a 
multiple-hole nozzle, differently from the exemplary embodiments described 
hitherto. 
FIG. 9 shows a variant of the combination of injection nozzle 16, adjusting 
drive 24, flow throttle 26 and nozzle accumulator 28 illustrated in FIG. 
8. In the variant according to FIG. 9, a channel 86 leads from the recess 
at the top end of the injection nozzle housing 52 to an annular chamber 88 
surrounding the nozzle needle 54, which is connected to the nozzle chamber 
56 by an annular gap 90 surrounding the nozzle needle, whilst the annular 
gap constitutes the flow throttle 26. The nozzle accumulator 28 is 
constructed in the injection nozzle housing 52 and connected to the nozzle 
chamber 56 by a channel 92. The function of the embodiment according to 
FIG. 9 is identical to the function of the embodiment according to FIG. 8. 
FIG. 10 shows a further variant of the combination of injection nozzle 16, 
adjusting drive 24, flow throttle 26 and nozzle accumulator 28 illustrated 
in FIG. 8, in which a way-valve 20 is additionally integrated in the 
injection nozzle housing 52. In the embodiment according to FIG. 10, the 
nozzle spring 18 has such a pretension that the nozzle needle 54 opens the 
injection orifice 58, constructed e.g., as a pintle nozzle, when the 
pressure of the fuel in the nozzle chamber 56 exceeds a specific value. 
The way-valve 20 which is thereby necessary is constructed as a 2/2 
way-valve in the exemplary embodiment illustrated, and exhibits as valve 
element the valve slide 72 which is connected firmly to the armature 60 of 
the adjusting drive 24 constructed as an electromagnet, and is arranged 
coaxially to the nozzle needle 54. The valve slide 72 blocks and opens the 
channel 84 between the flow throttle 26 and the nozzle chamber 56 when it 
respectively opens and blocks the communication between the inlet 76 and 
the outlet 78 of the way-valve 20. The injection starts when the adjusting 
drive 24 is modulated by the current impulse I and the way-valve 20 is 
thereby opened and the nozzle needle 54 raised, and ends when the pressure 
in the nozzle accumulator 28 has fallen below the closing pressure of the 
injection nozzle 16, or if the current impulse I ends previously. 
FIG. 11 shows a preferred exemplary embodiment of the arrangement of 
injection nozzle 16 and adjusting drive 24 which is suitable for the 
embodiments of the injection system according to FIGS. 1 and 2, although 
in FIG. 11 it is shown in conjunction with a preceding flow throttle 26 
and a nozzle accumulator 28 according to FIG. 2. 
In the nozzle pipe 14 downstream of the nozzle accumulator 28 and upstream 
of the injection nozzle 16 there is arranged a shut-off valve 94 which 
exhibits a valve element 96 which is loaded by a valve spring 98 in the 
direction of its closed position in which the valve element 96 maintains a 
control cross-section 100 closed, so that the nozzle pipe 14 is blocked. 
Constructed integrally with the valve element 96 is a control piston 102 
which is housed slidably in a control chamber 104 and is exposed to the 
pressure prevailing therein, whilst the pressure in the control chamber 
104 causes at the control piston 102 a force in the opening direction of 
the shut-off valve 94. 
The injection nozzle 16, the injection orifice 58 of which is constructed 
as a pintle nozzle, is maintained closed by its nozzle spring 18 until the 
pressure in the nozzle chamber 56 exceeds a specific value. 
Downstream of the nozzle accumulator 28 and upstream of the shut-off valve 
94 there is branched from the nozzle pipe 14, a pipe 106 in which a 
preliminary valve 108 is arranged which is actuated by the adjusting drive 
24, which is constructed as an electromagnet in the manner already 
described. The hydraulic preliminary control valve 108 exhibits a vavle 
element 110 which, due to the force of a valve spring 112, either 
maintains a control cross-section 114 closed or maintains a control 
cross-section 116 closed whilst the adjusting drive 24 is loaded by the 
current impulse I. 
The pipe 106 branched from the nozzle pipe 14 leads to the control chamber 
104. When the control cross-section 114 is closed, the pipe 106 is blocked 
and the control chamber 104 is connected by the control cross-section 116, 
then open, to an outlet 118. When, with the adjusting drive 24 modulated, 
the control cross-section 116 is closed, the control chamber 104 
communicates through the pipe 106 and the open control cross-section 114 
with the nozzle pipe 14, so that the pressure of the fuel in the nozzle 
pipe 14 prevails in the control chamber 104. 
When the adjusting drive 24 is modulated, therefore, the control chamber 
104 is loaded with pressure from the nozzle accumulator 28, so that the 
valve element 96 is slid upwards in FIG. 11 counter to the force of the 
valve spring 98 and opens the shut-off valve 94. Consequently the fuel 
pressure enters the nozzle chamber 56, so that the injection valve 16 
opens and the injection starts. The injection ends either when, during the 
injection, the fuel pressure in the nozzle accumulator 28 has fallen to 
the closing pressure of the injection nozzle and the nozzle needle 56 
closes the injection orifice 58, or when, at the end of the current 
impulse I, the valve spring 112 opens the control cross-section 116 and 
closes the control cross-section 114. This causes the pressure below the 
control piston 102 to fall, so that the control cross-section 100 is 
closed due to the force of the valve spring 98. 
As is clear from the above description, in the exemplary embodiment 
according to FIG. 11 the fuel to be injected does not flow through the 
preliminary control valve 108, so that the latter can be of considerably 
small construction and the masses to be moved by the adjusting drive 24 
are small. 
FIG. 12 shows a variant of the exemplary embodiment according to FIG. 11, 
for which reason only the differences from the exemplary embodiment 
previously described will be explained hereinbelow. 
In the exemplary embodiment according to FIG. 12 the pipe 106 issues into 
the nozzle chamber 56. Instead of the control piston 102 and of the 
control chamber 104 of the exemplary embodiment according to FIG. 11, the 
exemplary embodiment according to FIG. 12 exhibits a projection 120 shaped 
on the nozzle needle 54, against which the valve element 96 is braced. The 
actuation of the shut-off valve 94 therefore occurs by the nozzle needle 
54 during its upward stroke. 
When the control cross-section 114 is opened because the adjusting drive 24 
is modulated by the current impulse I, the pressure of the fuel in the 
nozzle accumulator 28 enters the nozzle chamber 56, so that the nozzle 
needle 54 is raised and thereby both opens the injection orifice 58 and 
also brings the shut-off valve 94 into its open position. The injection 
ends when the pressure in the nozzle chamber 56 has fallen below the 
closing pressure of the injection nozzle 16 due to the flow throttle 26, 
or when, at the end of the current impulse I, the control cross-section 
114 is closed and the control cross-section 116 is opened, so that the 
nozzle chamber 36 thereby comes to communicate with the outlet 118, which 
results in a lowering of pressure in the nozzle chamber 56 and hence 
closure of the injection nozzle 16. 
FIG. 13 shows a variant of the exemplary embodiment illustrated in FIG. 12, 
where the difference consists in the fact that in the exemplary embodiment 
illustrated in FIG. 13 the nozzle needle 54 and the valve element 96 of 
the shut-off valve 94 are integrally constructed so that the nozzle needle 
54 directly actuates the shut-off valve 94. The valve element 96 exhibits 
an annular groove 122 which cooperates with two annular grooves 124 and 
126 in the injection nozzle housing 52 so that the shut-off valve 94 
blocks the nozzle pipe 14 in the position shown in FIG. 13, whereas the 
annular grooves 124 and 126 communicate mutually through the annular 
groove 122 when the nozzle needle 54 and hence the valve element 96 have 
been raised after the pressure in the nozzle chamber 56 has been increased 
by the opening of the preliminary control valve 108. 
FIG. 14 shows a preferred embodiment of the fuel pump 2 of the injection 
system according to the invention. The fuel pump 2 is constructed as a 
multiple radial piston pump and comprises a pump housing 128 in which a 
pump axle 130 of cylindrical exterior is fixed. Mounted rotatably on the 
pump axle is a cylinder star 132 which is driven at constant speed ratio 
by the internal-combustion engine by means of coupling dogs 134 only 
schematically indicated. A plurality of radially oriented pump cylinders 
136 are constructed in the cylinder star 132 (see also FIG. 15), in which 
pump pistons 138 are slidably mounted, which are braced against the fuel 
pressure in the pump cylinders 136 against the cylindrical interior 
surface of a stroke ring 140. An eccentricity e exists between the axes of 
the stroke ring 140 and of the pump housing 128. The eccentricity e is 
equal to half the delivery stroke of each pump piston 138 and can be 
adjusted by means of an adjusting piston 142 which is arranged in the pump 
housing 128 slidably at right angles to the pump axle 130. Two pressure 
chambers 144 and 146 are constructed in the adjusting piston 142, between 
which a bracing piston 148 is present which is attached to the pump 
housing 128. During service the two pressure chambers 144 and 146 are 
charged with fuel, so that the adjusting piston 142 occupies a position 
determined by the equilibrium of the forces resulting from the pressures 
in the pressure chambers 144 and 146. 
A bore 150 is made coaxially in the adjusting piston 142 and is open 
towards the bottom end (in FIG. 14) of the adjusting piston 142. The 
adjusting member of the fuel pump 2, which is constructed as a control 
slide valve 152, is housed slidably in the bore 150. Annular grooves are 
made in the bore 150 and in the control slide valve 152 so that a total of 
five annular chambers 154, 156, 158, 160 and 162 and two annular webs 164 
and 166 are present on the control slide valve 152. 
The total flow rate Q of the fuel delivered by the fuel pump 2 is conveyed 
by the pressure pipe 6 into the annular chamber 158. The annular chamber 
158 is connected by an annular web 164 of specific throttle cross-section 
to the annular chamber 156 and further connected by an annular web 166 of 
specific throttle cross-section to the annular chamber 160. The magnitude 
of the two said throttle cross-sections is a function of the relative 
position between the adjusting piston 142 and the control slide valve 152. 
The annular chamber 156 is connected by a channel constructed in the 
adjusting piston 142 to the pressure chamber 144, so that the pressure 
prevailing in the annular chamber 156 is adjusted in the pressure chamber 
144. The annular chamber 160 is connected by a further channel constructed 
in the adjusting piston 142 to the pressure chamber 146, so that the 
pressure prevailing in the annular chamber 160 is adjusted in the pressure 
chamber 146. The annular chamber 156 is further connected by a throttle 
cross-section, likewise determined by the annular web 164, to the annular 
chamber 154, which is connected to the section of the pressure pipe 6 
leading to the collective pressure chamber 12. In similar manner the 
annular chamber 160 is connected by a throttle cross-section determined by 
the annular web 166 to the annular chamber 162, which is likewise 
connected to the section of the pressure pipe 6 leading to the collective 
pressure chamber 12. The total flow rate Q therefore travels through the 
adjusting mechanism of the fuel pump 2 along two separate paths: From the 
annular chamber 158 through the annular chamber 160 and the annular 
chamber 162 to the collective pressure chamber 12 and from the annular 
chamber 158 through the annular chamber 156 and the annular chamber 154 to 
the collective pressure chamber 12. 
When the control slide valve 152 is slid relatively to the adjusting piston 
142, the throttle cross-section between the annular chamber 158 and the 
annular chamber 156 on the one hand, and the throttle cross-section 
between the annular chamber 158 and the annular chamber 160 on the other 
hand, are modified in opposite directions. The throttle cross-sections 
between the annular chamber 156 and the annular chamber 154 on the one 
hand and the annular chamber 160 and the annular chamber 162 on the other 
hand are likewise modified in opposite directions. Irrespective of the 
relative position of the control slide valve 152 in the adjusting piston 
142, the overall throttle effect between the annular chamber 158 and the 
collective pressure chamber 12 is constant. In a central position of the 
control slide valve 152, in which the throttle cross-sections from the 
annular chamber 158 to the annular chamber 160 and from the annular 
chamber 158 to the annular chamber 156 are equal and the throttle 
cross-sections from the annular chamber 160 to the annular chamber 162 and 
from the annular chamber 156 to the annular chamber 154 are equal, the 
pressures in the pressure chambers 144 and 146 of the adjusting piston 142 
are equal, so that the latter assumes a stationary position and no 
adjustment of the eccentricity e of the stroke ring 140 occurs. In the 
case of positional deviation from this central position, pressure 
differentials appear in the pressure chambers 144 and 146, which lead to a 
resultant force at the adjusting piston 142 and hence to a displacement of 
the adjusting piston and hence in turn to a delivery stroke adjustment, 
until the symmetry of the relative position between control slide valve 
152 and adjusting piston 142 is re-established. The adjusting piston 142 
and the stroke ring 140 thus follow the position of the control slide 
valve 152, which can be moved without reactive forces from the fuel 
pressures acting upon it. 
FIG. 16 shows a further preferred embodiment of the fuel pump 2 of the 
injection system according to the invention, for which the same reference 
numerals are used for parts and elements which are identical to parts and 
elements of the exemplary embodiment according to FIG. 14; said parts and 
elements will not be explained afresh. 
In the embodiment according to FIG. 16 the adjusting piston 142 is 
constituted by a lower adjusting piston section 142a which projects into 
the pressure chamber 146 constructed in the pump housing 128, and by an 
upper adjusting piston section 142b which projects into the pressure 
chamber 144 constructed in the pump housing 128. The two adjusting piston 
sections 142a and 142b are arranged mutually coaxially and connected to 
the stroke ring 140, so that the pressures prevailing in the pressure 
chambers 144 and 146 act upon the adjusting piston in opposite directions. 
A spring 168 acting upon the adjusting piston section 142b is arranged in 
the pressure chamber 144, and a spring 170 acting upon the adjusting 
piston section 142a is arranged in the pressure chamber 146. 
The pressure chamber 144 is connected by a pipe 172 to the pressure pipe 6 
downstream of the fuel pump 2. Downstream of the branch point of the pipe 
172 there is arranged in the pressure pipe 6 a throttle valve 174 which 
exhibits a throttle cross-section 176 which can be modified by means of 
the adjusting member of the fuel pump 2, constructed as a control slide 
valve 152, so that a pressure differential exists between the pressures 
upstream and downstream of the throttle valve 174. Downstream of the 
throttle valve 174 a pipe 178 branches from the pressure pipe 6 and leads 
to the pressure chamber 146. The control slide valve 152 has such a form 
that the fuel pressures generate no resultant force upon it in its axial 
direction, so that the control slide valve 152 can be moved without 
reaction from the fuel forces. 
The adjusting piston 142a, 142b assumes such a position that the forces 
acting upwards and downwards (in FIG. 16) upon it are in equilibrium. 
Because a variable pressure differential can be adjusted between the 
pressures in the pressure chambers 144 and 146 by means of the throttle 
valve 174, the adjusting piston 142 follows the position of the control 
slide valve 152. 
FIG. 17 shows a variant of the exemplary embodiment illustrated in FIG. 16, 
in which parts and elements already explained are only schematically 
illustrated and not explained afresh. 
A shut-off valve 182, and a fixed throttle cross-section 184 in series 
therewith, are arranged in a pipe branch 180 parallel to the throttle 
valve 174. The shut-off valve 182 is actuated by an electromagnetic 
adjusting drive 186. When the shut-off valve 182 is in its blocking 
position A, the pipe branch 180 is blocked so that the variant according 
to FIG. 17 operates in the same manner as the exemplary embodiment 
according to FIG. 16. However, when the shut-off valve 182 is in its open 
position B, the pipe branch 180 is open so that by adjusting the shut-off 
valve 182 abruptly the pressure differential between the pressure chambers 
144 and 146 can be modified, which permits additional adjusting 
characteristics for the delivery stroke adjustment of the fuel pump 2. 
FIG. 17 also illustrates the electromagnetic adjusting drive 40 which acts 
upon the throttle valve 174, and the electronic control device 38, which 
have already been explained with reference to FIG. 2.