Fuel injection pump for internal combustion engines

A fuel injection pump for internal combustion engines is proposed, the work chamber of which has a relief channel which is controllable via an electromagnetically actuatable valve, the movable valve element of which is urged in a closing direction by means of the pressure which prevails in the pump work chamber.

BACKGROUND OF THE INVENTION 
The invention relates to a fuel injection pump for internal combustion 
engines of the type described in the preamble to the main claim. In a 
known fuel injection pump of this kind, the relief channel which 
determines the end of injection is controlled via distributor grooves and 
additionally by a magnetic valve. As a result, it is not possible to shut 
off the engine by shutting off the fuel injection quantity. In another 
known fuel injection pump, a magnetic valve is disposed in the channel 
which leads from the suction chamber of the pump to the pump working 
chamber, and by means of this valve the fuel supply of the pump working 
chamber can be interrupted in order to shut off the internal combustion 
engine. In both known cases, the distributor grooves substantially act as 
a pressure barrier between the pump working chamber and the valve, so that 
the closing springs of the valve or the strength of the magnet does not 
need to be adapted to the pump working pressure. 
OBJECT AND SUMMARY OF THE INVENTION 
The fuel injection pump according to the invention and having the 
characteristics of the main claim, in contrast, enables an opening of the 
relief channel before the beginning of the compression stroke, if this 
opening is required, and enables absolute tightness during the compression 
stroke so long as the valve is closed. 
The valve in accordance with the invention can be opened via the magnet 
either without electrical current or under the effect of electrical 
potential, where in the one case an opening force of a spring is overcome 
by the magnet causes the opening and in the other case it is the magnet 
itself which effects this opening. The use of a magnet-controlled valve 
can either serve to shut off the internal combustion engine or may act as 
a quiet-idling device, wherein a portion of the fuel flows out of the pump 
working chamber and as a result the injection time is lengthened, because 
a smaller quantity of fuel per unit of time proceeds to injection. 
The invention is not limited to the embodiment of the valve, but rather 
also pertains to the combination with characteristics of the structure 
and/or the purpose of its use. 
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 
Turning now to the drawings, a drive shaft 2 is supported in a housing 1 of 
a fuel injection pump for internal combustion engines with multiple 
cylinders. The drive shaft 2 is drivably associated with the end face of 
the cam disc 3, which is appropriately provided with four cams for example 
of a four cylinder engine to be supplied with fuel. The cams are moved 
over stationary rollers 5 as a result of the rotation of the drive shaft 
2. Consequently, a pump piston 8 coupled with the end face cam disc 3 by 
means of a coupler element 6 and pressed thereon by means of at least one 
spring is simultaneously set into reciprocal and rotary motion. 
The pump piston 8 operates in a cylindrical bushing 9 having a cylindrical 
bore 10 which is inserted into the housing 1 and closed at the top and a 
work chamber 11 is enclosed in the cylindrical bushing 9 by means of a 
pump piston 8. A valve body 12 serves to close the cylindrical bushing 9 
and with a movable valve element 13 represents a relief valve for the pump 
work chamber. The movable valve element 13 is under the influence of a 
closing spring 14, which presses a head 15 of the movable valve element 13 
onto a seat in the valve body 12. The head 15 is additionally pressed onto 
its seat by the pressure prevailing in the pump work chamber 11. A relief 
channel 16 is controlled by this valve and leads to a chamber in which a 
pressure prevails which is lower than the pressure prevailing in the pump 
work chamber 11 during the compression stroke. 
The movable valve element 13 is actuated by means of an electromagnet 17, 
which has a coil 18 and an armature 19 as well as a core 20. The housing 
21 of the magnet 17 is threaded into the housing 1 of the fuel injection 
pump, as shown, and via an expansible casing 22 holds the valve body 12 
firmly on the cylindrical bushing 9, so that certain variable expansions 
of the valve body, magnet housing and pump housing which occur when the 
temperature changes can be compensated for. In other words, as seen in the 
Figures, casing 22 is prestressed along its longitudinal axis between the 
housing 21 and valve 12. Due to this tight fit, which firmly holds the 
valve 12 on bushing 9, the casing is elastically deformed. If there are 
any occurrences of varying heat expansions, then the deformed portion of 
the casing 22 is capable of compensating for nonuniform variations in 
length, and it thus assures fundamental tightness of sealing under all 
operating conditions of the fuel injection pump. The casing thus has a 
function similar to that of an "anti-fatigue bolt." 
The pump work chamber 11 is supplied with fuel via a suction channel 23, 
which is controlled via suction grooves 24 disposed on the jacket surface 
of the piston 8. These suction grooves 24 open the suction channel 23 upon 
the occurrence of the suction stroke of the pump piston 8. The fuel supply 
is affected out of a suction chamber 25, which is disposed in the housing 
1 and in which a slight overpressure prevails. For the purpose of 
controlling the supplied fuel quantity, the work chamber 11 can be 
connected via an axial blind bore 26 in the pump piston 8 and a transverse 
bore 27 which intersects the blind bore with the pump suction chamber 25. 
A fuel supply quantity control member 28 in the form of an annular slide 
displaceable on the pump piston, cooperates with the transverse bore 27 
with the arrangement being such that the position of the annular slide 
determines the instant at which the transverse bore 27 opens during the 
upward movement of the pump piston 8 (compression stroke) and at which 
time a connection is established between the work chamber 11 and the pump 
suction chamber 25. 
By means of the adjustment of the annular slide 28, the quantity of fuel 
not proceeding to injection can thus be varied. In order to vary the fuel 
injection quantity, the annular slide 28 is adjusted by means of a control 
lever 30, which with a ball head 31 engages a recess 32 of the annular 
slide 28. The control lever 30 is pivotable about a shaft 34, which is 
adjustable by means of an eccentric 35. The other end of the control lever 
30 is engaged by a control spring, not shown, against the force of an rpm 
transducer. The initial stress of the control spring may be varied, for 
instance, by means of an adjusting lever which in turn can be adjusted 
arbitrarily. The rpm transducer then acts in the proper direction to 
reduce the fuel injection quantity when the rpm level is increasing, while 
the control spring acts in the direction of an increase in the fuel 
injection quantity. The rpm transducer may be a centrifugal force 
transducer or a hydraulic transducer. The particular balanced position 
which corresponds to a certain fuel injection quantity can be 
appropriately varied by means of the adjusting lever. 
The supply of fuel to the engine from the pump work chamber 11 takes place 
during the compression stroke and during the period when the transverse 
bore 27 is closed, fuel being supplied via the blind bore 26 which 
communicates via a transverse bore 36 with an annular groove 37, from 
which a distributor groove 38 branches off, by means of which in turn a 
pressure line 39 is opened. Pressure lines 39 are provided about the 
distributor piston 8 corresponding to the number of engine cylinders to be 
supplied; only one of these pressure lines 39 is shown in the drawing. 
During the rotation of the pump piston 8, the pressure lines 37 are opened 
by means of the lengthwise groove 38 one after another and are accordingly 
supplied with fuel from the pump work chamber 11, until the transverse 
bore 27 is opened by means of the annular slide 28 and the fuel can flow 
back from the pump work chamber 11, unused, into the suction chamber 25. 
In the exemplary embodiment shown in FIGS. 1 and 2, the fuel which flows 
out of the pump work chamber 11 via the valve 12, 13 flows out of the 
relief channel 16 into a channel 40, which terminates in the suction 
chamber 25. Thus, as soon as the valve 12, 13 is opened, the fuel flows 
unused back out of the pump work chamber 11 and into the suction chamber 
25, so that the engine is shut off. 
In the first exemplary embodiment shown in FIG. 1, the armature 19, when 
the magnetic coil 18 of the electromagnet 17 is excited, is pulled 
downward against the core 20 and is supported on the movable valve element 
13. During the compression stroke of the pump piston 8, the magnet 17 
cannot overcome the force in the compression chamber 11 which acts in the 
closing direction of the valve 12, 13. However, as soon as the pump piston 
8 begins its suction stroke, the magnet overcomes the force of the closing 
spring 14 and opens the valve 12, 13. During the subsequent compression 
stroke of the pump piston 8, no pressure can be established in the pump 
work chamber 11, so that the valve 12, 13 remains in the open position and 
all the fuel supplied by the pump piston 8 flows back, unused, into the 
suction chamber 25 via the channels 16 and 40. Even when because of 
dynamic throttle relationships between the head 15 and the valve body 12 
there are strong forces which act on the movable valve element 13 in the 
closing direction, which forces overcome the forces of the magnet, still 
during the next suction stroke the valve is again opened, so that the 
result is a great reduction in rpm and finally a shut-off of the engine. 
In a further three exemplary embodiments shown in FIGS. 2-4, corresponding 
structural elements have the same reference numerals as in the first 
exemplary embodiment; if there is a structural difference in the 
embodiment, the reference numeral is provided with a prime. 
In the second exemplary embodiment shown in FIG. 2, only the magnet and the 
valve drive thereby are shown. In contrast to the first exemplary 
embodiment, the core 20' of the magnet is disposed at the top and the 
armature 19' at the bottom toward the valve. When the coil 18 is excited 
the armature 19' is thus pulled upward against the core 20'. The armature 
19' has an inner bore which is closed at the bottom by a base 41 in which 
plural means defining openings 42 are provided for the purpose of pressure 
equalization. Between this base 41 and the core 20', an opening spring 43 
is disposed which when the magnet is not excited displaces the armature 
19' against the movable valve element 13', thus overcoming the force of 
the closing spring 14' and opening the valve 12', 13'. The stroke of the 
armature 19' is limited by an annular stop 44. There, as well, the opening 
spring 43 is able to open the valve only when the pump piston 8 completes 
a suction stroke. As soon as the coil 18 is excited the armature 19' is 
drawn upward with the force of the spring 43 being overcome, so that the 
closing spring 14' pulls the movable valve element 13' onto its seat and 
prevents the outflow of fuel via the channel 16. 
The coil 18 is switched on, for instance, via the ignition key of the 
engine, so that for starting the magnet is excited and thus an outflow of 
fuel through the relief channel 16 is prevented; thus, the engine can 
start. The shut-off of the engine then takes place by means of switching 
off the magnet 17; the ignition key breaks the electrical circuit, and 
subsequently the valve 12', 13' is opened by means of the spring 43 and 
the fuel supplied by the piston 8 flows, unused, back into the suction 
chamber 25, with the result that the engine is shut off. 
In the third exemplary embodiment shown in FIG. 3, the valve 12, 13 and the 
magnet 17 are embodied like those shown in the first exemplary embodiment 
in FIG. 1. In contrast to this first embodiment, however, the fuel 
diverted by means of the valve is conveyed through the throttle gap X via 
a channel 45 into a reservoir 46. The valve 12, 13 is opened only during 
idling and possibly at low partial-load, so that a portion of the fuel 
supplied by the pump flows into this reservoir 46, with the result that 
the injection time then taking place in the engine is lengthened. A 
lengthening of the duration of injection of this kind brings about a 
considerable reduction in engine noise; that is, so-called quiet idling of 
the engine is brought about. During the suction stroke of the pump piston 
8, a portion of the fuel located in the reservoir 46 flows back into the 
pump work chamber 11. This return flow can take place either via the 
relief channel 45 and the valve 12, 13 or via one of the suction grooves 
24; in the latter case, the channel 45 must have an appropriate extension 
47 oriented toward the bore 10. The magnet 17 may, for example, be 
controlled by means of a switch actuated with the accelerator pedal, so 
that the accelerator pedal position for idling and partial-load bring 
about a corresponding excitation of the magnet 17. 
In the fourth exemplary embodiment, shown in FIG. 4, in contrast to the 
third embodiment shown in FIG. 3, the reservoir is embodied as a spring 
reservoir 46'. The spring reservoir 46' functions by means of a reservoir 
piston 48, which is under the influence of a spring 49. While in the 
exemplary embodiment of FIG. 3, the reservoir capacity depends 
substantially on the elasticity of the fuel, in the exemplary embodiment 
shown in FIG. 4 the reservoir capacity is additionally determined by the 
stroke of the reservoir piston 48. 
In FIG. 5, a means of simplifying mounting is shown for the valve body 12". 
The valve body 12" has a threaded area 50 with few threads on its jacket 
surface; in the illustrated state, which is also the installed state, the 
threaded area 50 protrudes into an annular groove 51 which is disposed in 
the inner bore of the magnet housing 21'. A thread 52 is adjacent to this 
annular groove 51 on the side oriented toward the end of the bore. The 
valve body 12" is threaded into the magnet housing 21' by means of this 
thread 52, until the threaded area 50 is so disposed as to fit into the 
annular groove 51 without threaded engagement. During mounting or 
unmounting of the magnet, the valve body 12" and the casing 22 both remain 
together with the magnet housing 21. 
In the exemplary embodiment shown in FIG. 6, one controlled valve each is 
provided for shutoff and for prolonging the injection time. The movable 
valve element 13" serving to prolong the injection time is disposed in a 
valve element 54 serving the purpose of shutoff of the engine, and the 
valve element 54 is disposed in the valve body 12". The fuel quantity 
diverted for the purpose of quiet idling flows out via a channel 45", 
while the fuel diverted for the purpose of shutoff flows out via a relief 
channel 16". The channel 45", as in the exemplary embodiments described 
above, can discharge either into a reservoir or, throttled, into a chamber 
of lower pressure. In each case, the quiet-idle channel must always be 
openable first before a shutoff is undertaken. The magnet, of which only 
the armature 20" is shown here, is embodied as a two-stage magnet, which 
in the first stage, h.sub.1, opens the quiet-idle channel 45" and then in 
the second stage, h.sub.2, opens the relief channel 16". 
The valve element 13" is urged in the closing direction by a spring 14", 
which is supported on one end on a spring plate 55 connected to the valve 
element 13" and on the other end on the valve element 54. The valve 
element 54, in turn, is acted upon by a spring 56, which is supported on 
the valve body 12" and on a spring plate 57 at its respective ends. During 
the first stage, h.sub.1, of the magnet, only the spring 14" is 
compressed. Then, for the second stage, h.sub.2, the valve element 54 is 
displaced by the spring plate 55 against its spring 56. 
It is also conceivable that the valve members for shutoff and for quiet 
idling may function disposed beside one another, with the magnet in the 
first stage engaging only one member, and in the second stage engaging 
both members. 
The foregoing relates to preferred exemplary embodiments of the invention, 
it being understood that other embodiments and variants thereof are 
possible within the spirit and scope of the invention, the latter being 
defined by the appended claims.