U.S. patent number 3,680,535 [Application Number 05/081,221] was granted by the patent office on 1972-08-01 for fuel injection system for combustion engines.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Konrad Eckert, Heinrich Knapp, Gregor Schuster, Reinhard Schwartz.
United States Patent |
3,680,535 |
Eckert , et al. |
August 1, 1972 |
FUEL INJECTION SYSTEM FOR COMBUSTION ENGINES
Abstract
In an external-ignition combustion engine operating with
compression of the fuel mixture and continuous injection into the
suction duct fuel is measured off by a valve by means of a slider
actuated by a suction-responsive plate against a return force
provided by fuel pressure and subject to control in dependence on
operating characteristics of the engine. A pressure-control valve
may be subject to a spring bias which is varied by a surface cam in
response to throttle position and to pressure downstream of the
throttle in the suction duct. A further control in response to
engine temperature may be provided.
Inventors: |
Eckert; Konrad (Stuttgart-Bad
Cannstatt, DT), Knapp; Heinrich (Leonberg-Silberberg,
DT), Schwartz; Reinhard (Stuttgart-Sillenbuch,
DT), Schuster; Gregor (Stuttgart, DT) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DT)
|
Family
ID: |
5752568 |
Appl.
No.: |
05/081,221 |
Filed: |
October 16, 1970 |
Foreign Application Priority Data
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|
|
|
|
Dec 1, 1969 [DT] |
|
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P 19 60 144.6 |
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Current U.S.
Class: |
123/452; 123/453;
261/50.2 |
Current CPC
Class: |
F02M
69/22 (20130101); F02M 69/386 (20130101) |
Current International
Class: |
F02M
69/16 (20060101); F02M 69/38 (20060101); F02M
69/22 (20060101); F02M 69/30 (20060101); F02m
069/00 () |
Field of
Search: |
;123/119R,14CC,14MP,14MC,119,139 ;261/39A,69,5A,5AA,44,52 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Goodridge; Laurence M.
Assistant Examiner: Flint; Cort
Claims
That which is claimed is:
1. In a fuel injection system for an external-ignition combustion
engine operating on fuel injected into the suction duct and
including an arbitrarily operable butterfly valve disposed in said
suction duct, said system being of the known type that includes (a)
a fuel valve for metering the fuel quantities supplied to said
engine, (b) a sensor member forming part of an air sensor means and
being positioned in said suction duct spaced from said butterfly
valve, said sensor member being movable by and as a function of the
air flowing in said suction duct, (c) arm means forming part of
said air sensor means and being attached to said sensor member and
engaging said fuel valve for transmitting the motion of said sensor
member to said fuel valve to ensure the metering of fuel quantities
proportionate to the air quantities flowing in said suction duct
and (d) means for applying a substantially constant return force to
said sensor member, the improvement comprising
A. a movable member being in engagement with said air sensor means
and following the movements thereof and
B. means, including a pressure line, for continuously supplying
liquid under constant pressure to said movable member for urging
the latter against said air sensor means with a constant force
having a magnitude independent from the position of said air sensor
means and the position of said movable member, said means for
continuously supplying liquid under constant pressure and said
movable member constituting said means for applying a substantially
constant return force to said sensor member.
2. A fuel-injection system accordinG to claim 1, comprising at
least one pressure control valve responsive to an engine operating
characteristic for controlling the pressure of said liquid.
3. A fuel-injection system according to claim 2, in which said
pressure control valve is disposed in said pressure line downstream
of said movable member.
4. A fuel-injection system according to claim 1, in which said
movable member is coupled to said fuel valve.
5. A fuel-injection system according to claim 1, in which said
movable member comprises a slider operating in a cylinder in a
fluid-tight manner, said cylinder being connected to said pressure
line via a connecting channel having a restriction provided
therein, said slider having a radial face exposed to said constant
pressure.
6. A fuel-injection system according to claim 2, comprising means
for controlling the pressure of said pressure control valve in
response to deflection of said sensor member.
7. A fuel-injection system according to claim 2, comprising means
for controlling the pressure of said pressure control valve in
response to the pressure in said suction duct downstream of said
sensor member.
8. A fuel-injection system according to claim 2, comprising means
for controlling the pressure of said pressure control valve in
response to at least one temperature characteristic of said
engine.
9. A fuel-injection system according to claim 6, comprising a cam
movable in response to an engine operating characteristic to
control said pressure control valve.
10. A fuel-injection system according to claim 6, comprising a
surface cam movable in response to an engine operating
characteristic for controlling said pressure control valve.
11. A fuel-injection system according to claim 2, comprising
electric circuit means for transmitting an engine operating
characteristic to said pressure control valve.
12. A fuel-injection system according to claim 1, comprising means
for supplying fuel from said fuel valve as the liquid to said
pressure line.
13. A fuel-injection system according to claim 12, in which said
movable member responds to fuel pressure in said pressure line at a
point spaced in the direction of flow from said fuel valve.
14. A fuel-injection system according to claim 13, in which a
pressure-reducing means is provided between said fuel valve and
said point.
15. A fuel-injection system according to claim 5, in which said
movable member is a slider movable in a cylinder of said fuel valve
and having an annular notch cooperating with control slots provided
in said cylinder for measuring off fuel, said slider having an end
face extending into a chamber to respond to said liquid pressure
and a disc on said end face for damping movements of said
slider.
16. A fuel-injection system according to claim 15, in which spaces
are prOvided on both sides of said disc connected via individual
restriction channels with said pressure line.
17. A fuel-injection system according to claim 2, in which said
pressure control valve is a flat-seat valve having a biasing
spring, said biasing spring being responsive to an engine operating
characteristic for varying the bias thereof.
18. A fuel-injection system according to claim 17, in which the
movable valve member of said pressure control valve is a
diaphragm.
19. A fuel-injection system according to claim 18, in which both
sides of said diaphragm are subject to equal fuel pressures.
20. A fuel-injection system according to claim 2, comprising: a
bypass to said suction duct around said sensor member, a
temperature-responsive control element coupled to a pressure
control valve and to a closure member inserted in said bypass for
closing the same in response to the normal operating temperature of
said engine.
21. A fuel injection system according to claim 2, comprising
a first pressure control valve responsive to the position of said
arbitrarily adjustable throttle member and to the pressure
downstream thereof in said suction duct and
a second pressure control valve connected parallel with said first
pressure control valve and responsive to the engine temperature;
said first and said second pressure control valves vary the liquid
pressure generating said return force.
Description
FIELD OF THE INVENTION
The invention relates to a fuel-injection system for an
external-ignition combustion engine operating with compression of
the fuel mixture and continuous injection into the suction
duct.
BACKGROUND OF THE INVENTION
It is known to provide in such engines a sensor and an arbitrarily
adjustable throttle in longitudinally spaced arrangement in the
suction duct, the sensor being deflected against a substantially
constant return force in proportion to the rate of air flow to
control the movable member of a fuel valve for measuring off an
amount of fuel proportional to the amount of air.
In this type of fuel-injection system, it is desirable for the
deflection of the sensor to be as far as possible proportional to
the rate of air flow, so that a proportional amount of fuel can be
measured off by the fuel valve without complicated constructional
features having to be provided to assure the proportionality. This
requires that the return force of the sensor be as constant as
possible.
In the prior fuel-injection system of this type according to German
Pat. No. 1,281,746, a spring is provided to create the return
force. To obtain as accurate as possible a measurement of the rate
of air flow in the suction duct, the deflection of the sensor must,
however, be as large as possible. On the other hand, the return
force of a spring varies with the length of the spring, and in
order to provide reasonable constancy, the spring must be made very
weak and of great length, i.e. have a flat characteristic. This has
the disadvantage that the total size of the injection system
becomes comparatively large. Also, the force of the spring may vary
owing to transverse vibrations brought about by the engine. On the
other hand, it is impossible to provide a constant return force by
means of a short spring having a steep characteristic.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a fuel injection system
which does not exhibit the disadvantages referred to above.
This is achieved according to the invention by the use of pressure
liquid for creating the return force, the liquid being supplied
continuously at substantially constant pressure via a pressure line
to a movable member coupled to the sensor.
If it is now required to vary the fuel-to-air ratio, for instance,
in order to provide a richer mixture for starting the engine, this
can be achieved by a control of the return force on the sensor in
dependence on some operating characteristic of the engine. It is
known, for instance, from U. S. Pat. No. 2,583,408 relatinG to a
fuel-injection system having a spring for exerting a return force
on the sensor, to vary the bias of the spring in dependence on
temperature. In this connection, also, the use of a spring for the
return force has various drawbacks. For instance, the force is not
a linear function of displacement. Also, the spring must be
comparatively long and weak in order to provide under normal
operating conditions a substantially constant return force, but
this, on the other hand, requires the displacement for varying the
force of the spring to be correspondingly large. The size of the
arrangement becomes correspondingly large even at small energy
levels. Furthermore, the transmission of the engine characteristic
to the spring requires complicated mechanical constructions.
In a favorable embodiment of the invention, at least one pressure
control valve is provided downstream of the control member for
varying the liquid pressure of the return force in response to
operating characteristics of the engine.
Such an arrangement is advantageous in that the variation of the
liquid pressure does not have to occur in the vicinity of the
throttle but can be translated to any desired point by means of
conduits. If it is desired to control in dependence on throttle
position, the pressure control valve can be positioned close to the
throttle without the latter having to be close to the sensor, which
could lead to undesired aerodynamic interaction between these two
units. Thus, it becomes possible to place the sensor with the
measuring valve close to the air filter, which is practical in view
of their appreciable size, whereas the throttle can be located
immediately in front of the main part of the suction duct, from
which connections are branched off to the cylinders. A further
advantage is the incompressibility of the liquid, which makes for a
more exact control.
According to a further embodiment, the movable member is coupled at
least indirectly to the movable member or slider of the fuel valve,
the slider operating in a cylinder which is connected to the fuel
line via a channel having a restriction provided therein. This
damps the control movements of the slider and provides more uniform
engine operation.
In accordance with a still further embodiment, the liquid pressure
is controlled in response to throttle position and/or suction duct
pressure downstream of the throttle and/or at least one temperature
characteristic. A two- or three-dimensional cam or electric circuit
may serve to transmit such characteristics to the fuel valve. The
liquid pressure may be derived from the fuel supplied to the fuel
valve, preferably from a point longitudinally spaced therefrom. In
the latter alternative, a pressure-reducing valve may be inserted
between the fuel valve and the point in question, thereby providing
a pair of hydraulic circuits, one for measuring and one for the
return function. A pressure fluctuation in one circuit, e.g. owing
to fuel flow, then has little influence on the precision of the
control action of the other circuit.
The invention will be explained in more detail with reference to
embodiments thereof shown in the drawinG.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows an embodiment of the entire fuel injection system;
FIGS. 2, 3 and 4 show different embodiments of pressure control
valves;
FIG. 5 shows the arrangement of a pressure-reducing valve in the
fuel circuit;
FIG. 6 shows an hydraulic damping means for the moveble member of
the measuring valve;
FIG. 7 is a section taken on line VII--VII of FIG. 8 through a
pressure-reducing valve operating with a temperature-responsive
member which simultaneously controls a bypass of the suction duct;
and
FIG. 8 is a section taken on line VIII--VIII of FIG. 7.
Throughout the figures, identical parts are designated with
identical reference numerals. Primed reference numerals indicate
modified forms.
DESCRIPTION OF EMBODIMENTS
In the fuel injection system shown in FIG. 1, combustion air flows
in the direction of the arrows through an air filter 2 lodged in a
housing 1, a section 3 of a suction duct having a sensor 4 of a
measuring device therein, a connecting tube 5 and a section 6 of
the duct having an arbitrarily adjustable throttle 7, to one or
more cylinders of an internal combustion engine (not shown). Sensor
4 consists of a plate mounted perpendicularly to the direction of
flow but could also be a piston slidable perpendicularly to the
said direction or a shutter rotatable on a spindle traversing the
duct. In any case, sensor 4 moves in section 3 according to a
substantially linear function of the rate of air flow, the pressure
in the region between sensor 4 and throttle 7 being substantially
constant for a constant return force exerted on sensor 4 and a
constant air pressure ahead of sensor 4.
Sensor 4 immediately controls a measuring distributor valve 8. To
transfer the movements of sensor 4, there is provided an arm 10
attached thereto and pivoted with a minimum of friction on a pin 9.
Provided on arm 10 is a boss 11 for controlling the movable valve
member or slider 12 of measuring valve 8. The end face 13 of slider
12 remote from boss 11 is subject to the pressure of a liquid
serving as a return force for the sensor 4. The inoperative
position of arm 10 is defined by an adjusting screw 14.
Fuel is supplied by a fuel pump 16 driven by an electric motor 17
and drawing fuel from a container 18 and supplying it through a
fuel line 19 to measuring valve 8. From line 19 there branches off
a return line 20 having a pressure-limiting valve 21 provided
therein. The fuel flows from line 19 into a channel 22 in the
housing of measuring valve 8. Channel 22 ends in an annular notch
22a provided in the housing and from which borings 22b lead to a
cylinder 23 having a slider 12 fitting tightly therein. Borings 22b
terminate at a point of cylinder 23 at which slider 12 has a
peripheral notch 24 which is therefore connected without any
intermediate restriction to annular notch 22a. Notch 24 partially
overlaps a pair of control slots 25 to a greater or lesser extent
depending on the position of slider 12. From control slots 25 fuel
flows into channels 26 connecting with the injection valves (not
shown) in the suction duct of the engine. From annular notch 22a
the fuel not flowing into channels 26 flows into a channel 22c and
reaches an annular notch 22d from which it passes through borings
22e into a line 27 leading to a pressure control valve 28 and from
which a connection exists to cylinder 23 at the end face 13 of
slider 12. In this passage, a restriction 23a is provided for
damping the movements of slider 12. Also provided in channel
section 22c is a restriction for reducing as much as possible the
influence of pressure variations in the fuel measuring system on
the slider return system. Pressure control valve 28 is a diaphragm
valve 27a of the flat seat type with a diaphragm 29 as the movable
valve member. Already a minimal movement of diaphragm 29 is
sufficient to open the full annular valve area. The overflowing
fuel then flows without pressure through a line 30 back into fuel
container 18. Diaphragm 29 is biased by a spring 31, the force of
which is adjustable in response to a control effect derived in
dependence on engine operation. To this end, there is provided a
surface cam 32 which is rotatable jointly with throttle 7 and
axially displaceable in dependence on he degree of suction or
subpressure downstream of throttle 7 in the suction duct.
Surface cam 32 is axially displaceable on the shaft 33 of throttle
7, which is arbitrarily adjustable with the aid of a bar 34.
Rotation of shaft 33 is transferred by an angular catch member 35
to surface cam 32, which is journaled at one end thereof on a
diaphragm 36 of a suction chamber 37. Chamber 37 is connected via a
line 38 to a point in the suction duct downstream of the throttle.
If sufficient subpressure is present, cam 32 is displaced axially
by diaphragm 36 against the force of a return spring 39. The cam
surface is sensed by a pin 40, the movement of which is transferred
by a spring disc 41 on spring 31, the bias of which determines the
pressure for the return force on sensor 4.
Branching off from line 27 is a further line 67 connecting with a
second pressure control valve 68, from which it is returned without
pressure via a line 69 to fuel container 18. This valve controls
the pressure for the return force of slider 12 and sensor 4 in
dependence on engine temperature and comprises a flat-seat valve
70, the rate of flow of which is controlled by a diaphragm 71,
which is biased in the closing direction by a spring 72. The fuel
therefore flows through line 67 and valve 70 into a space 73 and
thence without pressure via return line 69 to container 18.
Container 18 is subject to atmospheric pressure and approximately
the same pressure is therefore present also in space 73. The space
74 separated from space 73 by diaphragm 71 and having spring 72
mounted therein forms part of a bypass 75, 75a for the throttle of
the suction duct and of which only the junctions with the suction
duct and with valve 68 have been shown. Provided in space 74 is a
slider 76 for controlling the bypass area and also serving as a
spring washer for spring 72.
Slider 76 is displaced by a temperature-responsive member, such as
a thermal-expansion device, 78 causing spring 72 to be less
compressed and bypass 75, 75a to be more open when the engine is
cold than when it is warm. Therefore, in a cold engine more liquid
flows through valve 70, the liquid pressure causing the return
force to be correspondingly lower and the fuel-to-air ratio of the
injected mixture higher.
The operation of the fuel-injection system for an engine that has
reached its normal operating temperature is as follows:
With the engine running, pump 16 is driven by motor 17 to draw fuel
from container 18 and supply it via line 19 to measuring valve 8.
Simultaneously herewith, the engine draws air through suction duct
3, 5, 6 and causes sensor 4 to be deflected from its inoperative
position.
Corresponding to this deflection of sensor 4, slider 12 is
displaced by arm 10 and uncovers a larger area of control slots 25.
The quantity of fuel supplied to the engine therefore varies in
dependence on the control effect derived from sensor 4. From
annular notch 24 the remaining fuel flows to the terminal side of
slider 12 and therefrom to pressure control valves 28 and 68.
The direct coupling of sensor 4 with slider 12 results in a
constant fuel-to-air ratio if the characteristics of these two
members are sufficiently linear, which is the desired type of
operation. The fuel-to-air ratio would then be constant over the
entire operating range of the engine. As was indicated above,
however, it is desirable to make the fuel mixture richer or thinner
according to the section of the operating range of the engine. This
is achieved, according to the invention, by varying of the return
force acting on sensor 4.
As quantities that are indicative of engine loading and rpm there
are available the throttle position and the suction duct
subpressure and it is therefore convenient to derive the return
force from these. This is achieved by means of a variation of the
force of spring 31 of pressure control valve 28 occasioned by a
corresponding rotational or axial displacement of surface cam 32 in
dependence on the position of throttle 7 and the pressure in the
suction duct, respectively. For instance, if the throttle at full
load is in a position in which the suction duct is fully opened, it
is desired to have the highest output power, i.e. a relatively rich
mixture. Since the bias of spring 31 of control valve 28 determines
the pressure acting on the end face 13 of slider 12, the return
force acting upon sensor 4 must be reduced by a small amount to
cause displacement of slider 12 to a position in which control
slots 25 are more open and a correspondingly larger amount of fuel
is injected. Contrarily, in the section of the operating range
corresponding to a partially loaded state, the relatively higher
pressure on the end face 13 of slider 12 results in a smaller
deflection of sensor 4 and a correspondingly thinner mixture.
On the other hand, in the passive part of the operating range, with
the engine being pushed by the vehicle, a strong subpressure is
present in the suction duct and surface cam 32 is pushed far ahead
against spring 39 causing a strong bias to be exerted by spring 31
of the pressure control valve. This increases correspondingly the
return force on sensor 4, whereby in spite of the small amount of
leakage air flowing around the closed throttle, there is no
deflection of sensor 4 and no injection of fuel.
As long as the engine is cold, pressure control valve 68 causes an
enrichment of the fuel mixture, since the pressure from which the
return force is derived is now lower. Owing to the fact that a
portion of the air flows through bypass 75, 75a, sensor 4 is
deflected more than what corresponds to the throttle position, so
that already on account of this deflection a greater amount of fuel
is measured off.
The pressure of the fuel acting on end face 13 of slider 12 and
causing the return force on sensor 4 is therefore maintained
inherently constant and is varied only in dependence on engine
characteristics, such as in the embodiment shown, the position of
the throttle, i.e. in dependence on the load, as well as the
subpressure in the suction duct, i.e. in dependence on the rpm.
FIG. 2 shows the portion of the system comprising the pressure
control valve. In this embodiment, the bias of spring 31 of control
valve 28' is controlled by a cam 43, which is displaceable only
axially in response to the pressure obtaining downstream of the
throttle in the suction duct. To this end, cam 43 is mounted on
rollers 44. The control movement is transferred in this case also
to spring washer 41 by a pin 40. The throttle therefore is now in
no way coupled to the cam. The adjustment of the bias of spring 31
and therefore the return force on sensor 4 is therefore dependent
on rpm and load.
In the FIG. 3 embodiment, on the other hand, pin 40 is controlled
by a cam 46 which is mounted on shaft 33 of throttle 7, whereby
upon shaft 33 being rotated by operation of bar 34, pin 40 is
displaced by cam 46. In this case therefore, there is a variation
of the return force on sensor 4 in dependence only on the load.
In the FIG. 4 embodiment of the pressure control valve, the bias of
spring 31 is varied by a surface cam 32, just as in FIG. 1.
However, there is a difference in that there is provided in
diaphragm 29' an aperture 48, through which fuel can flow from line
27 and the space 49 delimited by diaphragm 29' into the space 50 in
which spring 31 is mounted and from there via line 30' back to
container 18. This causes the pressure of container 18 to be
present on both sides of diaphragm 29, whereby a possible
fluctuation in the pressure of the fuel container has no control
effect on the diaphragm.
In order to handle larger corrections by meanS of the pressure
control valve, there is provided in the FIG. 5 embodiment of the
measuring valve 8' in channel section 22c' a pressure reducinG
valve 52 shown as a simple diaphragm valve, the diaphragm 53 of
which is subject on one side to the supplied fuel and on the other
side to a spring 54 in combination with the atmospheric pressure
entering through an aperture 55.
To prevent the slider of the measuring valve from being pushed back
and forth by possible pressure shocks which might be transferred to
it from the suction duct via sensor 4 and lead to fluctuations in
the rate of injection and jerky behavior of the vehicle, FIG. 6
shows an embodiment 8" of the measuring valve in which the movement
of slider 12" and therefore also that of sensor 4 is braked and
damped by means of a disc 57 placed on the end face of slider
12".
To this end, slider 12" extends with its end face 13 into a
cylindrical space 58 of approximately the same diameter as disc 57
and which is divided thereby into spaces 58a and 58b connected with
each other by means of damping borings 23a and 60 to channel 22c.
Since the surface of disc 57, which is subject to the fuel pressure
in space 58a, is larger than the surface facing space 58b, borings
23a and 60 must be proportioned to have equal damping effects in
both directions of slider 12".
In the embodiment shown in FIGS. 7 and 8, pressure control valves
28 and 68 of FIG. 1 have been constructionally integrated into a
pressure control system 28". In this case also, spring 31' can be
controlled by means of a surface cam 32'. In addition, however,
there is provided for transmitting the engine temperature a thermal
expansion regulator 62 for controlling spring 31'. Regulator 62
acts via slider 63 on one arm of a two-armed lever 64, the pivot
point 64a of which is coupled to spring 31', and the other arm of
which is in engagement with surface cam 32'. Lever 64 is guided by
means of a link 65 attaching it to the housing. Slider also
controls an idling channel 66 which, similarly to FIG. 1, connects
a point upstream of the throttle in the suction duct with a point
downstream thereof. With increasing temperature, slider 63 is
pushed towards a position in which the bias of spring 31' and
therefore also the return force on sensor 4 increases.
The invention can be used in any type of system where a suction
duct draws in an amount of air, to which there is to be admixed a
corresponding amount of a liquid, for instance, in chemical
apparatus, gasoline heating systems and power turbines.
* * * * *