Fuel injection device for auto-ignition internal combustion engines

A very compact and inexpensive fuel injection device for auto-ignited internal combustion engines can be mounted on existing internal combustion engines to replace conventional fuel injection devices. The fuel injection device has one or more high-pressure pumps (10) that feed fuel into a supply tank (11) from which the fuel may be supplied through proportioning valves (16) to injection valves (15, 15'). The pressure in supply tank (11) is maintained by an automatic control system for the high-pressure pumps (10), the outputs of which are controlled by a control rod (13) that adjusts a plunger (18) of the high-pressure pumps (10) provided with a slanting edge (17).

TECHNICAL FIELD 
This invention relates to a fuel injection device for an autoignition 
internal combustion engine having a crankshaft rotatably supported in a 
crankcase, to which crankshaft there is articulated at least one 
connecting rod bearing a piston, the piston being movable in a cylinder 
covered by a cylinder head, the fuel injection device having at least one 
high-pressure fuel-conveying pump, which conveys the fuel into a supply 
reservoir (common rail), which is connected to at least one injection 
valve via at least one proportioning valve. 
BACKGROUND OF THE INVENTION 
Such a fuel injection device is known from the brochure "Reliable 
Electronic Injection with Future Fuel Qualities" of the MAN company, dated 
April 1980. The fuel injection device described in the beforementioned 
brochure is designed for use with a two-stroke marine diesel engine. This 
fuel injection device has a fuel pressure reservoir, from which the fuel, 
at an approximately constant pressure of approximately 700 bar, can be 
withdrawn under electronic control for delivery to the individual 
injection valves. This entire control is constructed so that, in addition 
to the electronic control, it further requires a working fluid in the form 
of a hydraulic fluid, with which the individual valves and control 
elements are actuated. Further, the components "cylinder unit and 
high-pressure pump," which are illustrated at least approximately to 
scale, are arranged far apart so that, together with the fuel pressure 
reservoir arranged at another location on the internal combustion engine, 
long connecting lines are needed for the pressurized fuel. Because of the 
long lines, the system as a whole is hydraulically soft, so that the 
advantages achievable in principle with the illustrated fuel injection 
system are not achieved. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is an object of the invention to create a fuel injection device for an 
autoignition internal combustion engine, which fuel injection device is 
made hydraulically stiff and compact in construction. 
According to the invention, this object is achieved by virtue of the fact 
that the high-pressure pump is inserted into the crankcase and is arranged 
with its high-pressure side in a region near a cylinder and is driven from 
a camshaft on its drive side. This design, in development of the fuel 
injection device of the stated type, creates an injection device that is, 
as a whole, made mechanically and hydraulically very stiff, from the 
camshaft drive, through the arrangement and alignment in the crankcase, up 
to the arrangement of the high-pressure delivery as close as possible to 
the injection valve or to the supply reservoir interposed or integrated 
into the cylinder head, and that improves the injection behavior of the 
internal combustion engine according to the invention relative to the 
prior art. Exactly definable and controllable injection behavior is 
especially important with regard to low fuel consumption and favorable 
emission behavior of the internal combustion engine. Both the exhaust 
emissions of the internal combustion engine and also its noise emissions, 
insofar as they are influenced by the injection device, are reduced. A 
hydraulically stiff system is definitely important especially when a 
supply reservoir is used, since it is the total injection quantity per 
working cycle, which with this system can, for example, be split into a 
pre-injection quantity and main injection quantity, that must be metered 
most accurately. Weaknesses in the injection system, even those that would 
be unobjectionable in a conventional system, have very detrimental impact 
in an injection system where the total injection quantity is split into a 
pre-injection quantity and a main injection quantity. 
In development of the invention, the high-pressure pump is inserted without 
enclosure into the crankcase. This design has the advantage that, on the 
one hand, a separate enclosure for the high-pressure pump is saved and, on 
the other hand, the entire system becomes mechanically stiffer by this 
means, since space is saved by means of the elimination of a separate pump 
enclosure, which space can be employed for a reinforcement of the 
crankcase in this region. The otherwise necessary fits or connections of 
the pump enclosure to the crankcase are also eliminated by virtue of the 
elimination of the separate pump enclosure, which has an impact at least 
with regard to the machining effort. 
In development of the invention, the high-pressure pump is an injection 
pump element having edge control. This design permits the use of already 
available and tested pump elements, with which, moreover, it is made 
certain that these can deliver the required pressures in the range of 
approximately 1400 bar. Edge control, furthermore, permits accurate and 
reliable control of pressure in the supply reservoir without costly 
overpressure and drain valves being necessary in the supply reservoir. 
These elements can be saved by means of active control of the charge 
pressure of the supply reservoir. 
In development of the invention, the camshaft has cams for breathing valve 
actuation and is driven from the crankshaft via a single gear engagement. 
This design is advantageous particularly in an in-line internal combustion 
engine, since by this design a separate camshaft for driving the 
high-pressure pump is saved. Also, the camshaft is advantageously designed 
so that three cam segments are arranged directly next to one another at 
least in partial regions along the camshaft and are bracketed by bearings. 
Here two cam segments are needed for the control of the breathing (intake 
and exhaust) valves, while the third cam segment is used for actuation of 
the high-pressure pump. The camshaft is further stiffened by means of the 
bracketing of these segments by bearings, so that sources of error 
stemming from flexure or torsion of the camshaft are nearly eliminated. 
The bearings and the cam regions lying therebetween can also be made to 
transition from one to the other in a transitionless fashion, that is, 
without recesses. A further contribution to a stiff camshaft is made by 
this design having a minimum space requirement. Torsions of the camshaft 
relative to the crankshaft, which occur in known camshaft drives via a 
plurality of gears, toothed belts or chains, and which reduce the 
achievable peak pressure to impair exact control, are averted by the drive 
of the camshaft from the crankshaft by a single pair of meshing gears. 
In development of the invention, the camshaft has two, three or a plurality 
of cam distributed over the periphery of the camshaft for driving the 
high-pressure pump. This design has the advantage that the high-pressure 
pump can charge the supply reservoir a plurality of times upon a single 
rotation of the camshaft. In contrast to an injection pump element, the 
charging of the high-pressure reservoir is independent of what operating 
stroke is in progress, to which operating stroke the injection pump 
element together with the injection valve must be aligned. Furthermore, 
the flanks of the cam can be reshaped in that the steep flanks required 
for injection pump elements are made less sharp for the supply reservoir 
supply pumps, since--as already discussed above--no steep pressure rise is 
required with high-pressure pumps as is required with injection pump 
elements for compliance with specified injection laws. Instead, the cams 
can be optimized with respect to the loading of the high-pressure pump and 
of the entire system. The number of cams arranged on the periphery of the 
camshaft therefore depends on the particular circumstances of the internal 
combustion engine (number of cylinders, size of high-pressure pump, etc.). 
In development of the invention, two or more high-pressure pumps are 
arranged along the internal combustion engine. Here again, what was stated 
before holds: that optimization is done in accordance with the 
aforementioned parameters (number of cylinders, delivery volume of the 
high-pressure pump, etc.). 
In development of the invention, the supply reservoir extends along at 
least one cylinder row of the internal combustion engine. By this 
construction, in cooperation with the already discussed close arrangement 
and alignment of the high-pressure pump to a cylinder head having the 
assigned injection valve, a further contribution is made to a stiff 
system, since the length of the connections from high-pressure pump to 
supply reservoir and from supply reservoir to the individual injection 
valves are shortened to the greatest possible extent by this construction. 
If the internal combustion engine is of the V type, a single supply 
reservoir can, according to the invention, be arranged in the V-shaped 
space between the two cylinder rows, this design suggesting itself 
particularly in the case of small V angles, that is, when the two cylinder 
rows are aligned relatively close together. Otherwise, it is also 
contemplated in the context of the invention to provide two supply lines, 
one supply reservoir then being assigned to one cylinder row. The supply 
reservoir(s) can also advantageously be integrated into the cylinder head. 
In development of the invention, the supply reservoir is connected to the 
high-pressure delivery of the high-pressure pump via a short pressure 
line. By this design, as already indicated, the losses or pressure 
fluctuations that occur with long pressure lines are virtually eliminated. 
In further development of the invention, the supply reservoir is borne by 
two or a plurality of high-pressure pumps. This design is desirable 
especially when, for example, there are two or three high-pressure pumps 
that are distributed along the internal combustion engine, for example at 
the two ends and in the middle of a cylinder row, the supply reservoir 
then being attached directly to these high-pressure pumps. As an alternate 
design, a complete unit consisting of high-pressure pumps and supply 
reservoir can be preassembled, and mounted as a unit on the internal 
combustion engine. This eliminates the separate attachment of a supply 
reservoir. 
The proportioning valve may be arranged on the supply reservoir or it may 
be placed on the injection valve. The arrangement is chosen that best 
suits the existing requirements. Thus a proportioning valve arranged 
directly on the injection valve can control the quantity of fuel being 
proportioned to the injection valve very accurately in terms of quantity 
and time, since no lines negatively impairing proportioning are present 
between the proportioning valve and the injection valve. On the other 
hand, a proportioning valve arranged on the supply reservoir again offers 
the possibility of creating a very compact unit, also to be prefabricated 
or preassembled, consisting of high-pressure pump, supply reservoir and 
proportioning valves. Moreover, the required height is reduced by means of 
the elimination of the proportioning valve in the region of the cylinder 
head, which height is scarcely available in many applications. In 
development of the invention, the proportioning valves can be at least 
largely solenoid-actuated valves, which already find use in convention 
solenoid-valve-controlled injection systems (MV systems of the Deutz AG). 
These are systems in which the injection pump element is provided with 
such a solenoid-actuated valve that controls the quantity of fuel to be 
delivered to an injection valve connected to an injection pump element or 
solenoid-actuated valve. Piezoelectric switching elements can also be 
employed in order to actuate the proportioning valves. 
In development of the invention, the pressure prevailing in the supply 
reservoir is employed for controlling the high-pressure pump. Suitable for 
this purpose is the already described design of the high-pressure pump 
with a pump plunger that has a control edge, this control edge then being 
connectable to corresponding drain holes by a control rod. The pressure 
prevailing in the supply line acts via a hydraulic and/or electric 
transmission on a control element that then actuates the control rod 
positioning the control edges. In the simplest embodiment, the supply line 
can be provided, for example at the end face, with a pressure transmission 
line, which opens into the control element made as a pressure transducer 
and that controls the control rod for positioning the control edges. 
Alternatively, however, the pressure in the supply reservoir can also be 
picked off electrically or via sensors and this measured value can be 
employed for positioning the control rod. An appropriate positioning 
motor, for example a stepping motor, can be used for this purpose. In just 
the same way, however, it is also possible to employ the electrical 
signals for driving a hydraulic positioning mechanism of the control rod. 
In development of the invention, the control element is arranged at an end 
face of the internal combustion engine, in particular in place of a speed 
governor. This design has the advantage that no additional space 
requirement on the internal combustion engine is needed in order to mount 
such a control element. Instead, the internal combustion engine as a whole 
can be made such that it is optionally equipped with a conventional 
injection system with or without the above-described solenoid-actuated 
valve hardware, however, with the system having a supply reservoir 
according to the invention. 
Finally, in development of the invention, the control element is inserted 
in an opening in the crankcase in place of an injection pump element. As 
already stated, not all of the openings present in a conventional internal 
combustion engine will be needed for the injection pump elements of the 
invention, since fewer high-pressure pumps are required in order to 
generate the necessary high pressure in the supply reservoir. Thus, the 
control element can be inserted in an unused injection pump opening. This 
control element is then constructed similarly, in principle, to a 
high-pressure pump, however it does not have a drive from the camshaft. 
Instead, the pressure transmitted hydraulically and/or electrically from 
the supply reservoir is then transmitted "quasi-backward" to the control 
rod for controlling the delivery quantity of the other high-pressure 
pumps. This design represents a particularly compact embodiment, this 
construction also being employable as support for the supply reservoir 
according to one of the previous designs. 
The fuel injection device according to the invention can also be 
implemented with ordinary plug-in pumps. Here the injection pump element 
or the high-pressure pump is arranged in its own pump enclosure. This pump 
enclosure can be arranged chiefly in the crankcase of the internal 
combustion engine or partially in and partially on the same, and can have 
an external fuel supply in contrast to the fuel supply advantageously 
arranged in the crankcase in the design previously described. This 
arrangement offers the advantage that the high-pressure compartment of the 
high-pressure pump can be applied to the injection valve in close 
cooperation with the supply reservoir. Also, the danger of fuel heating 
and fuel leakage inside the crankcase is averted by use of the external 
fuel.

DETAILED DESCRIPTION OF THE INVENTION 
The autoignition internal combustion engine 1 shown schematically in FIG. 1 
has, in the exemplary embodiment, six cylinders which are arranged in a 
row. The internal combustion engine 1 is substantially conventionally 
constructed and has a crankshaft 2, which is supported in a crankcase 3 
(see also FIGS. 2 and 3). Further supported in the crankcase 3 is a 
camshaft 4, the camshaft 4 being driven by the crankshaft 2 via a single 
gear engagement, that is, a pair of mating gears. For this purpose, gears 
5a, 5b are arranged on the ends of the crankshaft 2 and the camshaft 4, 
which gears are designed so that the camshaft 4 is driven at half the 
speed of the crankshaft. The camshaft 4 has breathing-valve cams 6a, 6b 
assigned to each cylinder, adjoining which cams are further cams 7a, 7b, 
7c, which are positioned in the same axial region of the camshaft 4 as the 
breathing valve cams 6a, 6b and lying on the periphery of the camshaft 4 
(FIGS. 2 and 3). The breathing valve cams 6a, 6b and the cams 7a, 7b, 7c 
are bracketed by bearings 8a, 8b, which are directly adjacent to the 
breathing-valve cam 6a and the cams 7a, 7b, 7c. The transition from the 
bearings 8a, 8b to the individual cam regions takes place in a 
transitionless fashion, that is, essentially without recesses between the 
bearings and cams and without recesses between the individual cam regions. 
In FIG. 1, the bearings 8a, 8b with the cam regions lying therebetween are 
also shown only for one cylinder, similarly to the way the crankshaft 2 is 
shown in only a partial region. Both components in the illustrated design 
extend over the entire length of the internal combustion engine 1. 
Referring also to FIG. 2, a roller tappet 9 of a high-pressure pump 10 
rides on the cams 7a, 7b, 7c of the camshaft 4 and drives a pump plunger 
18, which conveys fuel via a short pressure line 12 into a supply 
reservoir 11 (common rail) extending along the internal combustion engine 
1. In terms of its basic construction, the high-pressure pump 10 includes 
an injection pump element having edge control. In other words, the 
previously mentioned pump plunger 18 has a control edge 17, which 
cooperates with a drain hole, depending on the rotation of the pump 
plunger 18. By this rotation, the delivery quantity of the high-pressure 
pump 10 can be varied between a zero delivery quantity and a maximum 
delivery quantity. The pump plunger 18 is positioned by a control rod 13, 
which extends along the internal combustion engine 1. 
During operation of the internal combustion engine, fuel is continually 
conveyed by the high-pressure pump 10 into the supply reservoir 11. 
Injection lines 14 corresponding to the particular number of cylinders in 
the internal combustion engine 1 branch off from this supply reservoir 11, 
which injection lines are ultimately connected to an injection valve 15. 
According to the exemplary embodiment of FIG. 2, the supply reservoir 11 
is mounted on and attached to the crankcase 3 or the cylinder bank. The 
injection lines 14 branching off from this supply reservoir 11 open into a 
proportioning valve 16 mounted on the injection valve 15. This 
proportioning valve 16 is designed, for example, as a solenoid-actuated 
valve controllable by an electronic control unit, which solenoid-actuated 
valve controls the fuel flow from the injection line 14 into the injection 
valve 15 in accordance with the respective operating parameters. 
In distinction to the exemplary embodiment of FIG. 2, the supply reservoir 
11 in the exemplary embodiment of FIG. 3 is attached directly to the 
high-pressure pump 10. Further, the proportioning valve 16 is in turn 
arranged directly on the supply reservoir 11, so that the injection line 
14' opens directly into the injection valve 15'. The possibility of 
arranging the proportioning valve 16 directly on the injection valve 15 
also exists in this exemplary embodiment. By use of the illustrated design 
of the internal combustion engine having a supply reservoir 11, the fuel 
is available in the supply reservoir at an approximately equal pressure 
of, for example, 1400 bar under virtually all operating conditions, and 
can be delivered via the proportioning valves 16 to the injection valves 
15, 15' in a virtually arbitrarily controlled fashion. The running 
behavior of the internal combustion engine, in particular the exhaust 
emissions and noise emissions, and also the fuel consumption, can be 
positively influenced by this construction. 
As previously discussed, the quantity to be delivered by the high-pressure 
pumps 10 is controlled by the pump plunger 18 provided with the control 
edge 17, which plunger is positioned rotatively by the control rod 13. The 
axial displacement of the control rod 13 effecting positioning is carried 
out by a control element in the form of a pressure transducer 19, which 
according to FIG. 1 is arranged on the end face of the internal combustion 
engine. This pressure transducer 19 is connected to the supply reservoir 
11 via a control line 20. This system is tuned so that, if the pressure in 
the supply reservoir 11 decreases, this falling pressure is passed on to 
the pressure transducer 19 via the control line 20 and the pressure 
transducer 19 accordingly positions the control rod 13 so as to increase 
the delivery quantity of the high-pressure pumps 10. Simple automatic 
pressure control in the supply reservoir 11 is possible by this mechanism. 
In the context of the invention, the pressure in the supply reservoir 11 
can also be picked off, for example by means of pressure sensors, and 
these signals passed on to the pressure transducer 19. The pressure 
transducer 19 in this case is preferably designed as an electrically 
actuated control element. As described in the general description, it is 
also provided in the context of the invention to insert the control 
element in the form of a pressure transducer 19' into an opening in the 
crankcase 3 of the internal combustion engine next to a high-pressure pump 
10, in a manner similar to insertion of the pump. This control element is 
designed substantially similarly to a high-pressure pump 10 but it has no 
roller tappet 9. Instead, the pressure in the supply reservoir is 
transmitted by the control line 20' to the control element which in turn 
positions the control rod 13.