U.S. patent number 3,595,013 [Application Number 04/794,187] was granted by the patent office on 1971-07-27 for compensated supercharging devices for compression-ignition engines.
This patent grant is currently assigned to Societe Anonyme De Vehicules Industriels et D'Equipements Mecaniques. Invention is credited to Yves M. Baguelin, Maurice G. Brille.
United States Patent |
3,595,013 |
Brille , et al. |
July 27, 1971 |
COMPENSATED SUPERCHARGING DEVICES FOR COMPRESSION-IGNITION
ENGINES
Abstract
A compensated supercharging device for a compression-ignition
engine cooled by a liquid at a regulated temperature and already
supercharged by a turbosupercharger, said device tending to correct
the known inconveniences of this type of supercharging by
regulating the temperature and pressure of the air delivered by
said turbosupercharger before it is introduced into the engine for
all speed and load conditions of said engine.
Inventors: |
Brille; Maurice G. (Suresnes,
FR), Baguelin; Yves M. (Suresnes, FR) |
Assignee: |
Societe Anonyme De Vehicules
Industriels et D'Equipements Mecaniques (Suresnes (Hauts de
Seine), FR)
|
Family
ID: |
27444964 |
Appl.
No.: |
04/794,187 |
Filed: |
January 27, 1969 |
Foreign Application Priority Data
Current U.S.
Class: |
60/599; 123/561;
60/609 |
Current CPC
Class: |
F02B
39/04 (20130101); F02B 37/14 (20130101); F02B
37/04 (20130101); F02B 39/00 (20130101); F02B
39/08 (20130101); F02N 19/00 (20130101); F02B
27/04 (20130101); Y02T 10/12 (20130101); Y02T
10/144 (20130101); Y02T 10/146 (20130101) |
Current International
Class: |
F02B
27/00 (20060101); F02N 17/00 (20060101); F02B
39/08 (20060101); F02B 37/04 (20060101); F02B
39/04 (20060101); F02B 27/04 (20060101); F02N
17/08 (20060101); F02B 37/12 (20060101); F02B
39/00 (20060101); F02B 37/14 (20060101); F02B
39/02 (20060101); F02b 037/04 () |
Field of
Search: |
;60/13 ;123/119C |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hart; Douglas
Claims
We claim:
1. A compensated supercharging device for a compression-ignition
engine cooled by a liquid at a regulated temperature and already
supercharged by a turbosupercharger, said device tending to correct
the known deficiencies of this type of supercharging by regulating
the temperature and pressure of the air delivered by said
turbosupercharger before it is introduced into the engine for all
speed and load conditions of said engine, said device comprising a
duct connecting said turbosupercharger to said engine, a heat
exchanger in said duct, means for circulating an engine cooling
liquid through said heat exchanger at a regulated temperature, a
volumetric air machine mounted in said duct between said exchanger
and said engine, transmission means operatively connecting said
volumetric air machine to a crankshaft of said engine so that the
ratio of the speeds of said air machine and said engine will vary
continuously between two limits, one of said limits producing an
output volume of the machine which is greater than the engine
cylinder cubic capacity so as to produce an over pressure and the
other of said limits producing an output volume of said machine
which is lower than that of said engine cylinder cubic capacity so
as to expand the air pressure, a control diaphragm operatively
connected to said transmission means to control said speed ratio
variation in response to a reference pressure resulting from a
predetermined combination of pressure prevailing upstream of said
volumetric air machine and pressure prevailing downstream thereof,
said speed ratio variation being controlled inversely to changes in
said reference pressure.
2. A device as set forth in claim 1 in which said supercharger
comprises a high efficiency turbosupercharger having the highest
possible pressure ratio at maximum engine speed.
3. A device as set forth in claim 1 wherein said volumetric air
machine comprises a gear pump having at least two teeth.
4. A device as set forth in claim 1 in which said transmission
comprises a belt-type variable-speed transmission having at least
one variable-diameter grooved pulley, a swivel shaft means
connecting said pulley to volumetric air machine, said swivel shaft
means comprising a bearing, a universal joint and a resilient
support, said swivel shaft means being relatively long so that the
maximum amplitude of its swivel movements cannot exceed
.+-.3.degree., the movements of the pulley flanges towards and away
from each other being controlled by said reference pressure.
5. A device as set forth in claim 1 in which said transmission is
of the hydraulic type and comprises a hydraulic pump and hydraulic
motor assembly of the piston-barrel and swash-plate type, the speed
variation resulting from the action exerted by said reference
pressure on the inclination of said swash plate.
6. A device as set forth in claim 3 further comprising special
starting means provided when said gear pump is rendered inoperative
as a consequence of internal leakages at very low engine speeds,
notably at engine starting speeds, said starting means being
adapted, during the rotation of a starter motor of said engine, to
inject upstream of said gear pump a liquid capable of adhering by
surface tension to the internal surfaces of said pump so as to
temporarily seal the leakages thereof, said injection means
comprising a jet disposed at the inlet end of said duct, an
electromagnetic valve and a liquid supply, the circuit for
energizing said electromagnetic valve being established from a
storage battery and said starter motor and comprising a switch
responsive to a thermostatic control diaphragm capable of opening
said circuit when the temperature of the engine cooling liquid has
reached a sufficient value.
7. A device as set forth in claim 6 in which said sealing liquid
comprises engine fuel supplied from the engine fuel feed pump.
8. A device as set forth in claim 3, further comprising means for
minimizing the influence of leakages by increasing very
considerable proportions the drive ratio of said gear pump, said
means momentarily uncoupling said transmission and substituting
therefor a direct step up gear providing a higher gear ratio, said
uncoupling being controlled by a drive pinion of a starter motor
through a linkage, the direct step up gear being obtained by the
meshing action of said starting motor drive pinion on a tooth wheel
mounted on a shaft of said volumetric air machine.
Description
This invention relates in general to means for supercharging
compression-ignition engines and has specific reference to devices
for producing the compensated supercharging of engines of this
character.
It is the chief object of this invention to provide a device
capable, , in a compression-ignition engine already supercharged by
a turbosupercharger, or producing substantially unchanged
temperature and pressure conditions for the air introduced into the
cylinders, regardless of the conditions of operation of the engine.
The ultimate object is to obtain controlled combustions in all
cases, that is, a high-efficiency and low-consumption engine,
without releasing smoke at low speeds nor emitting aldehydes at
low-loads and when starting the engine, even in the case of
multifuel engines, while preserving a torque curve ensuring a
reliable driving power and without endeavoring to obtain a constant
power output.
It is now current practice to supercharge Diesel or
compression-ignition engines by using a turbosupercharger driven
from the exhaust gases.
This technique is advantageous not only on account of the reduced
overall dimensions and low weight of the means involved, but also
in that it permits improving the engine power output by utilizing a
substantial fraction of the energy usually lost with these gases,
in spite of the counterpressure created by the turbine. A cooling
system arranged between the supercharger and the engine further
improves the engine cylinder filling.
In many cases the supercharging is completed by a more or less
strong scavenging action by causing the opening times of the inlet
and exhaust valves of a same cylinder to more or less overlap each
other. Thus, the temperature of the pistons is reduced, so that
they can withstand the considerable supercharging stress.
However, these various arrangements cannot be exploited as much as
desired for the following reasons:
1. The turbosupercharger efficiency is higher at high engine
speeds, so that the torque curve is deflected in a direction
opposite to the usually desired direction;
2. At low load values the counterpressure may exceed the feed
pressure, thus creating a counterscavenging likely to prove
detrimental to the useful life of the inlet valve;
3. It is rather difficult to select a suitable volumetric ration
combining a maximum pressure limitation and an easy starting.
It is the object of this invention to provide a device capable of
preserving full load fuel conditions in all cases arising during
the operation of a Diesel or compression-ignition engine already
supercharged by a turbosupercharger, and more particularly of
providing constant combustion conditions by regulating the
induction air temperature and pressure, notably by expanding this
air when the engine revolves at full-power and reinforcing the air
supercharging when the engine operates at low speed or under
low-load conditions.
The device according to this invention, which can be used in a
compression-ignition engine equipped with cooling system utilizing
a liquid as a heat transfer medium, and with a turbosupercharger
driven from the exhaust gas and connected to an induction manifold
or pipe of the engine, is characterized by the following
features:
A temperature and pressure corrector is interposed in the
scavenging duct and comprises a heat exchanger through which the
cooling liquid of the engine is caused to flow, and a volumetric
pump driven from the engine shaft through a variable-speed
transmission adapted to be uncoupled. This transmission is so
controlled through means responsive to force depending on the air
pressure prevailing in the scavenging duct, that the corrector
tends to increase the quantity of air fed downstream of the pump
when this pressure is low and on the contrary to decrease this
quantity of air when said pressure is high. An uncoupling and
coupling control device may be associated with the transmission and
with the starter motor so that the operation of the starter motor
will disconnect the transmission and couple the pump to the driving
pinion of the starting motor.
The corrector will thus act as a pressure-reducing device at high
power outputs, and as a supercharger at low loads.
Thus, a turbosupercharger of the high pressure ratio type can be
used for at high engine power output values the assembly comprising
the supercharger, the heat exchanger and the pressure-reducing
device acts as a real refrigerator which, in combination with a
reasonable volumetric ratio in the engine, permits maintaining the
pressure and temperature values, at the end of the compression
stroke, within predetermined limits.
At low loads when the turbosupercharger gives neither sufficient
pressures nor sufficient temperatures, the heat exchanger through
which the engine cooling liquid adjusted at a constant temperature
is caused to flow will then act as a reheater and the volumetric
pump will further increase the temperature as it increases the air
pressure, whereby the combustion conditions approximate those
obtained under full load. This pressure increment further permits
overcoming the exhaust gas pressure and avoiding any counter
scavenging action. Of course, the conditions of operation of the
volumetric pump must be adapted to vary gradually from one limit to
another by passing through a neutral point at which it will neither
compress nor expand the air, this neutral point corresponding, for
example, to the conditions which would have been selected for
supercharging the engine by means of a turbosupercharger if no
corrector were provided.
The control means responsive to a force depending on the air
pressure prevailing in the scavenging duct may advantageously be
actuated by a pressure-responsive pick up element mounted in said
duct upstream of the volumetric pump, in combination or not with a
similar pick up element mounted downstream of said pump. The pick
up element or elements may consist of a pressure-responsive capsule
of the diaphragm or piston type branched off the manifold. The
force of the movable member of the capsule is then utilized for
varying the transmission ratio.
The correcting volumetric pump consists preferably of a gear-type
supercharger (without excluding blade- or vane- or piston-machines)
driven preferably through the medium of a variable-speed
transmission of the type comprising variable-diameter pulleys and
belts. A hydrostatic transmission may also be used with a
variable-output pump and a fixed-output hydraulic motor. The main
point to be adhered to is that this transmission, for reasons to be
set forth presently, can be uncoupled automatically, for example in
a first case by the movement of the flanges of two pulleys away
from each other and in another case by operating a bypass valve in
the hydraulic circuit. The extreme speed ratio will be at the most
1:1.7, so that the variable-speed transmission can be designed
under the best possible conditions from the dual point of view of
efficiency and simplicity.
Another important feature characterizing this invention lies in the
particular use made of the corrector during the engine starting
period. It was observed that at low engine speeds and loads,
notably when idling is indulged in, the device according to this
invention acted as a reheater. One might reasonably think that the
same applies to the engine starting period, but in this case the
centrifugal supercharger produces no pressure, the liquid in the
heat exchanger is cold and the volumetric pump, notwithstanding the
maximum step-up ratio provided by the transmission, does not rotate
fast enough, in spite of its leakages, for producing a sufficient
pressure and temperature increment; therefore, it is proposed to
increase very strongly the rotational speed of the pump during this
period by uncoupling same from the transmission and driving this
pump directly from the starter motor, in conjunction with the
engine and in the same fashion, by means of the starter motor
pinion driving a toothed wheel mounted on the pump shaft and
similar to the conventional toothed ring mounted on the flywheel,
but of a diameter so calculated that the momentary transmission
ratio thus obtained between the engine and the pump is several
times greater (e.g. 3, 4 or 5 times) than the maximum step up ratio
provided by the variable-speed device. Thus, the pump speed will be
sufficient to create a certain overpressure and more particularly
an appreciable temperature increment, as the leakages are recycled.
The volumetric pump can be uncoupled from the variable speed
transmission by mounting the former of a freewheel device, but this
arrangement would preclude its use as a pressure reducing device at
high power outputs; preferably, a clutch associated with the
variable-speed device will be used, this clutch being driven from
the starter motor and constructed for example in the manner set
forth hereinabove.
The power requirement of the starter motor is not necessarily
increased since the resulting overpressure and the reheating of the
piston crowns will reduce the necessary engine torque.
This invention is further concerned with means capable of improving
the efficiency of the corrector during the engine starting periods
as an alternative and a substitute for the corrector coupling and
step up system described hereinabove, by eliminating or reducing
the air leakages mentioned in the foregoing, which leakages are
normally observed between the movable members and between these
members and the case of the volumetric pump. To this end, an
injection device fed with a surface-active liquid capable of
adhering to said movable members and under a pressure greater than
that prevailing in the scavenging duct opens into this duct
upstream of the pump, this injection device comprising on the one
hand a passage for said liquid which has a cross-sectional area
calculated to cause the liquid output therethrough to momentarily
stop any air leaks, and on the other hand, a stop of valve member
permitting the flow of said liquid towards said duct only during
the engine starting periods.
Thus, any air leaks from the pump are eliminated during the
starting period by injecting upstream of the pump, with a moderate
output, a liquid capable of adhering by surface-tension to the
rotors and thus momentarily stop or cut off any leakages.
The above-mentioned surface-active liquid may consist of a suitable
oil, but it is preferable to use the engine fuel proper. In fact,
this liquid will finally penetrate into the engine and it is
preferable to burn it without leaving any harmful deposit therein.
The scavenging of this liquid efficiently atomized by the pump
action will create a kind of vapor which, associated with the
normal pump injection, promotes the fuel combustion.
Of course, this fuel injection should not continue after the engine
has actually been started, and therefore it must be stopped
immediately as the engine fires. Preferably, a suitable
electromagnet-valve may be used for controlling this injection,
this valve being energized to its open position in conjunction with
the starter motor.
Finally, when the engine has warmed up the device becomes useless;
it may even prove detrimental and cause in this case untimely
preignitions.
It is therefore advantageous that the energizing circuit of the
electromagnet valve be controlled by a thermostat responsive to the
engine cooling water temperature, the circuit being open when the
water is hot.
These multiple arrangements tending to keep the pressures and
temperatures as constant as possible at the end of the engine
compression stroke in all operating conditions are favorable to the
engine operation as a multifuel engine.
It is important to not that what characterizes this invention in
comparison to known combinations of centrifugal supercharger with
volumetric supercharger as utilized for instance in certain
large-sized two-stroke engines is that the corrector is not
synchronized with the engine, that its controlled drive causes this
corrector to operate as a pressure-reducing device and/or as a
supercharger, that its position downstream of the heat exchanger
disposed in turn downstream of the centrifugal supercharger causes
this device to operate now as a cooling device or as a reheater,
and that when it acts as a pressure reducing device it returns a
certain amount of energy to the engine.
This invention is also concerned with various additional
constructional details which will appear as the following
description proceeds with reference to the accompanying drawings,
in which:
Fig. 1 illustrates diagrammatically, as a function of the engine
speed, the curves corresponding to the pressure ratios of the
turbosupercharger under various loads corrected and uncorrected by
the corrector of this invention;
Fig. 2 is a diagram showing the assembly with a variable speed pump
drive of the belt-and-pulley type;
Fig. 3 is a cross-sectional view of the pump;
Fig. 4 illustrates the same general diagrammatic view as FIG. 2,
the variable speed drive of the pump being of the hydrostatic
transmission type;
Fig. 5 shows in elevational view a compression-ignition engine
equipped with a modified type of variable-speed belt transmission
having only one variable-diameter pulley;
Fig. 6 illustrates in the same engine as shown in FIG. 5 in plane
view;
Fig. 7 is a section taken along the line VII-VII of FIG. 6;
Fig. 8 is a side elevational view of the engine as seen in the
direction of the arrow VIII of FIG. 6;
Fig. 9 illustrates a modified form of embodiment of the variable
drive illustrated in FIG. 2;
Fig. 10 is a detail view as seen along the section line X-X of FIG.
9;
Fig. 11 illustrates diagrammatically a compression-ignition engine
supercharged and equipped with a starting injection device, and
Fig. 12 is a view showing on a larger scale the starting injection
device proper.
Referring first to FIG. 2, it will be seen that the
compression-ignition engine 1, preferably of the four-stroke cycle
type, comprises an exhaust pipe 2 directing the exhaust gas towards
the rotor 3 of a radial turbine driving via a shaft 4 the rotor 5
of a centrifugal supercharger. The scavenging duct 6 of this
supercharger has inserted therein the corrector of this invention
which comprises a heat exchanger 7 and a volumetric pump 10. Thus,
the compressed air will be directed by the scavenging duct 6
firstly through the heat exchanger 7 in which the engine cooling
fluid regulated at a constant temperature is circulated from an
inlet 8 to an outlet 9, the through the volumetric pump 10 shown in
cross-sectional view in FIG. 3. This pump is a conventional
volumetric gear pump delivering combustion air to the engine 1 via
the inlet pipe 11 and manifold 12. The pump shaft 13 is coupled to
the engine crankshaft 14 by means of a variable-speed transmission
of any known type, such as fluid, electrical or friction
transmissions. The transmission illustrated is a pulley-belt
arrangement comprising a V-belt 15 according to the know
arrangement; the flanges 16 and 17 of the pulleys receiving this
belt are keyed to shafts 13 and 14 respectively, and the pulley
flanges 18 and 19 registering with the flanges 16 and 17
respectively and driven at the same speeds are slidably movable to
a moderate extent in the axial direction whereby the diameter of
the portion engaged by the belt 15 on each pulley can be varied. In
the specific case contemplated, which requires but a moderate
variation in the extreme speed ratios (e.g. from 0.85 to 1.5 ) the
two flanges 18 and 19 can be moved simultaneously in opposite
directions by a rocker 20 engaging with one end 21 and flange 18
and with the opposite end 22 the flange 19, for example by means of
thrust bearings. This rocker 20 is fulcrumed intermediate its ends
to a strap 23 urged by a spring 24; it is actuated at 21 by a
control diaphragm 25 counteracted by a compression spring 26. This
control diaphragm 25 is supplied with air under a variable pressure
through a line 27 connected through a gauged air orifice 29 to a
branch line 28 leading from duct 6 at the outlet of the heat
exchanger and through another gauged orifice 31 to another branch
line 30 leading from pipe 11 at the outlet of the volumetric pump
10, a third air orifice 32 being inserted in said line 27 and
communicating with the external atmosphere.
The extension 36 of shaft 13 of the volumetric pump 10 carries a
toothed wheel 37 having the same teeth as the toothed ring 38 of
the engine flywheel, the pinion 39 of the starter motor being
adapted to mesh simultaneously with both gears, provided that their
teeth are designed with a suitable contour. The dimensions of these
two gears are such that the speed step up ratio between the engine
1 and pump 10 is greater than the highest gear ratio provided by
the variable-speed transmission incorporating the belt 15. The
starter motor is equipped with means for uncoupling the
variable-speed belt transmission; in this example, said means
comprise a linkage shown in diagrammatic form as comprising levers
40 and 41 adapted to compress the above-mentioned spring 24 and
thus simultaneously eliminate the belt-tensioning effort exerted by
both flanges 18 and 19. Another means may consist in compressing
said spring 24 by using an electromagnet energized in conjunction
with the starter motor.
A hydrostatic transmission of the type illustrated in FIG. 4 may be
substituted for the belt-type variable-speed transmission. In this
case, the engine crankshaft 14 drives a barrel piston pump 42
having its output per revolution regulated by a fixed swashplate
43. The shaft 13 of pump 10 is then coupled to a hydraulic motor 44
also of the barrel piston type, of which the output per revolution
is made variable by the variable inclination of the relevant
swashplate 45. This variable inclination of swashplate 45 is
controlled by a pressure-responsive control diaphragm 46
communicating with the scavenging duct 6 via line 27. These two
hydraulic units are interconnected by passages 47 and 48 adapted to
be interconnected in turn by a bypass line provided with a control
valve 49 operable by means of a linkage (shown in diagrammatic form
at 50) from the starter motor pinion 39. If desired, the movable
swashplate 45 may also be mounted without any inconvenience on the
hydraulic unit 42, only the control means thereof being modified
accordingly.
The operation of the above-described arrangement will now be
explained with reference to FIGS. 1 and 2, it being assumed that
only air orifice 29 is operative.
Let us assume that P.sub.1 is the air pressure at the inlet of the
centrifugal supercharger, P.sub.2 the pressure between this
centrifugal supercharger and the volumetric pump, P.sub.3 the
pressure between this volumetric pump and the engine. In FIG. 1 the
engine speed is plotted in abscissa against the pressure ratios
P.sub.2 /P.sub.1 and P.sub.3 /P.sub.1 plotted in ordinates; the
thick line curves designate the variation in the ratio P.sub.2
/P.sub.1 at different load values, and the dash line curves show
the variation in the ratio P.sub.3 /P.sub.1 also at different load
values.
The values .alpha. of the pump/engine speed ratio are also shown in
ordinates.
With a maximum of 100 percent load, at an engine speed a
representing substantially the three-fourths or the four-fifths of
the maximum engine r.p.m. value, the pump/engine speed ratio is so
selected that the volume generated by the pump corresponds to the
engine cylinder filling capacity; in other words and to simplify
the disclosure, let us assume that this ratio is 1.00. At this
point the unit operates as if no corrector were provided; the
pressures P.sub.3 and P.sub.2 are identical and the thick and
dashline curves intersect each other at a point A corresponding to
said engine speed a.
The ratio P.sub.3 /P.sub.1 equals P.sub.2 /P.sub.1 is relatively
high; assuming that the temperature A at the outlet of the
supercharger as in excess of 100.degree. C., it is reduced to about
80.degree. C. by the heat exchanger 7 and preserves this value in
the manifold 11 as it penetrates into the engine.
If the engine speed increases, the ration P.sub.2 /P.sub.1
increases with the pressure P.sub.2. Assuming that the air jet 31
were not perforated, the increment in pressure P.sub.2 would be
transmitted via duct 28, jet 29 and line 27 to the diaphragm 25
which would load the thrust bearing 21 while unloading the thrust
bearing 22 by means of a rocker or compensator 20, thus causing a
reduction in the pump/engine speed ratio .alpha., for example down
to 0.85 at speed b. The volume generated by the pump is lower than
the engine filling capacity; pressure P.sub.3 (at point B') is
lower than the pressure P.sub.2 (at point B, FIG. 1). The output
temperature of the supercharger, which was for instance 150.degree.
C., is reduced to about 100.degree. C. at the outlet of heat
exchanger 7, and then to about 80.degree. C. in the manifold 11
after the expansion of the volumetric pump 10. Thus, from the point
of view of combustion, the conditions thus obtained approximate the
operating conditions at point A.
If in contrast thereto the engine speed decreases the ration
P.sub.2 /P.sub.1 decreases with the pressure P.sub.2. The control
diaphragm 25 receiving this pressure as before relieves the
thrust-bearing 21 while loading the other thrust-bearing 22, thus
augmenting the pump/engine speed ratio .alpha. for example up to
1.15 for an engine speed c. The volume generated by the pump is
greater than the engine cylinder filling capacity; the pump acts as
a second stage of a supercharger. The pressure ratio P.sub.3
/P.sub.1 (at point C') is higher than pressure ratio P.sub.2
/P.sub.1 (at point C). The temperature at the outlet of the first
supercharger stage, which may have been 50.degree. C., is increased
by the heat exchanger to about 60.degree. C. and then to about
100.degree. C. by the second supercharging stage 10. Thus, normal
operating conditions are restored. In all the cases contemplated
the scavenging action takes place normally.
The operation takes place as in the preceding example when the
engine speed is d with a load reduced for example by 50 percent,
the pump operating as a supercharger with a pressure P.sub.3
/P.sub.1 at D' considerably greater than pressure P.sub.2 /P.sub.1
at D. The temperature, after the two reheatings by the exchanger 7
and the pump 10, attains a relatively high value approximating
100.degree. C.
The combustion conditions are nearly the same as at full load.
Moreover, the counterscavenging effect usually feared at low loads
cannot occur due to the high pressure P.sub.3 at D'.
In the above-description of a typical mode of operation, P.sub.2 is
selected as a single criterion of the control-diaphragm operation;
in some instances one may introduce correcting elements from
pressure P.sub.3 by properly gaging the air orifices 29 and 31.
This kind of constancy in the combustion conditions permits so
selecting these conditions that the engine can be operated as a
multifuel engine without any risk of overstressing it.
The energy transmitted through the variable speed transmission of
the pump circulates in one or the other direction according to
whether the pump operates as a supercharger or as a
pressure-reducing device. In no case high-power values are
transmitted; however, in the supercharging direction these values
are the highest when the engine power output values are the lowest.
It should be noted that in this case the transmitted power is
partly returned on the pistons. Since the above-defined ratio
P.sub.3 /P.sub.1 remains always relatively low, the supercharger
efficiency is satisfactory and the actual loss very moderate. This
loss is amply compensated by the combustion improvement, so that
the overall efficiency of the engine at low engine loads is
satisfactory. The reduction in fuel consumption in all
engine-operating conditions constitutes one of the objects of this
invention, but nevertheless the first objects are on the one hand
the improvement in the power-to-weight ratio and the possibility of
operating the engine on any fuel.
When starting the engine the operation is as follows:
The starter drive pinion 39 is moved to the left as seen in FIG. 2
so as to mesh both with gear ring 38 and toothed wheel 37, their
teeth being shaped accordingly; at the same time it reacts against
the strap 23 through linkage 40, 41 while compressing spring 24.
The V-belt 15 is no longer tensioned against one of its pulleys.
The pump 10 is driven only by toothed wheel 37. The pump 10 may be
so designed that it does not produce any additional torque for
"unsticking"the engine; as the latter begins to rotate the
considerable gear ratio provided by the pump drive causes the pump
to create a certain pressure P.sub.3 in pipe 11, of course with
considerable leakage and a certain reaction torque. The temperature
in said pipe 11 increases to a substantial degree, considering
however the compression and the recycling of air leaks. Therefore,
the cylinder walls and the lubricating oil are heated, and the
temperature at the end of the compression stroke is increased very
strongly. Immediately as the engine is started, the engine torque
available at the gear ring 38 assisted by the force of spring 24
will push back the starter drive pinion 39 in the known manner
while the V-belt 15 causes the pump 10 to be driven again under
normal conditions.
In the arrangement shown in FIG. 4, the functions of the
variable-diameter pulleys 16--18 and 17--19 are provided by the
hydraulic pump 42 and motor 44, the hydraulic motor 44 being of the
variable-capacity type. When the engine is started, the linkage 50
associated with the starter drive pinion 39 opens the bypass valve
49 to short circuit the pump 44 and the corrector 10 is then driven
through the toothed wheel 37 as in the preceding example.
In order to simplify, and reduce the cost of, the V-belt and pulley
variable-speed transmission described hereinabove and illustrated
in FIG. 2, a single variable pulley transmission illustrated in
FIGS. 5 to 8 of the drawings may be used.
According to this invention, this alternate form of embodiment is
characterized by the following specific features:
The variation in diameter for controlling the transmission ratio by
means of this belt and pulley device applies only to the driven
pulley driving the pump;
This driven pulley acts at the same time as a belt-tensioning
device;
The belt-tensioning pulley is responsive to a spring blade acting
at the same time as a resilient pulley-supporting bracket;
The shaft carrying the driven pulley of the transmission is coupled
through a single universal joint to the pump shaft and its length
is relatively long so that the maximum amplitude of its swivel
movements cannot exceed .+-. 3.degree. in order to minimize on the
one hand the angular amplitude of driven member of this universal
joint and on the other hand the angular variation of the plane of
said pulley. Therefore, a single ball bearing is sufficient for
supporting the shaft at the pulley end and besides the radial
reaction at the pump shaft is negligible, so that it is not
necessary to fit a relatively large rolling-contact bearing in this
pump, as contrasted with conventional arrangements wherein the belt
tension is exerted on the driven end of the pump;
The angular variation in the shaft position is attended by a very
moderate torsion of the spring blade, so that the stress produced
in this plane is very slight;
The variation in the plane of the driven pulley of the transmission
is kept within very reasonable and permissible limits;
Finally, the pneumatic system controlling the movement of one
flange of this pulley in relation to the other is mounted directly
on the pulley with its return compression spring, the control air
being supplied thereto through a flexible pipe.
As will be seen in FIGS. 5 to 8 to four-stroke compression-ignition
engine 1 is supercharged by a turbosupercharger 52 connected
through a scavenging pipe 6 to to one orifice of a Rootes-type
volumetric pump 10. The other orifice of this pump communicates
with the induction manifold 12 of the engine. The heat exchanger of
the corrector, normally interposed in this pipe 6, is not
shown.
The pump shaft 13 is connected through a universal joint 53 to a
hollow shaft 54 rigid with a shaft 55 carrying the right-hand
flange 56 of the driven pulley, as shown in FIG. 5. The stub end 57
of this shaft 55 is mounted in a single ball bearing 58 carried by
a case 59. This case 59 is secured to the outer end of a spring
blade 60 having its other end anchored by means of a bracket 61 to
the wall 62 of the engine cylinder-block (FIG. 8).
A sleeve 63 rigid with the left-hand flange 64 of the pulley is
slidably mounted on shaft 55. The tubular shaft 54 has formed at
its pulley end an integral flange to which one end of a control
diaphragm or bellows 66 is welded, the opposite end of this control
diaphragm being welded to the left-hand flange 64. A compression
spring 67 is enclosed in the control diaphragm and constantly urges
the sliding or movable flange 64 against the V-belt 15.
The inner chamber of control diaphragm 66 communicates via an axial
passage 68 of shaft 55 with the line 27 of FIG. 4 or with lines 27,
28 and 30 of FIG. 2. The pressure obtaining in the control
diaphragm 66 assists the spring 67 in the lateral clamping of
V-belt 15 between the pulley flanges. As can be seen, the flange 65
of shaft 54, the control diaphragm 66 and the pulley flange 64
constitute a pressure-responsive diaphragm or bellows like the
devices 25 and 46 illustrated in FIGS. 2 and 4 respectively.
The V-belt 15 is mounted on the other hand on a grooved pulley 69
keyed on the crankshaft of engine 1.
The spring blade 60 is cut to a shape imparting a substantially
uniform resistance thereto, so that it can clear the pulley 56, 64
while exerting a constant force substantially in the plane of this
pulley.
To maintain the movement of the driven pulley in the position shown
by the axis 72 in FIG. 8 a link 70 is pivoted at one end to a very
light bracket or arm 71 and at the other end to the bearing case
59.
This alternate form of embodiment of the variable transmission
operates as follows:
When the air pressure created for regulation purposes within the
control diaphragm 66 through a flexible pipe increases so as to
strongly compress the V-belt 15 by moving the pulley flange 64
toward its companion flange 56 while compressing the spring 60, the
belt 15 engages a greater diameter of these pulley flanges 56, 64
so that the pulley tends to move downwards, i.e. towards the engine
crankshaft. Under these conditions the shaft 54 moves but through a
very small angle easily accepted by the universal joint 53, without
appreciably altering the momentary angular velocities involved.
Similarly, the median plane of this pulley 56, 64 varies by the
same angular amplitude also accepted by the belt 15.
It will be noted that the acceptance of these small angular
movements is attended by the following advantageous
simplifications:
A single universal joint is used,
A single ball bearing is necessary,
The supporting bracket is merged into the spring blade (the guiding
system 70,71 being extremely simplified),
A single inlet joint for supplying air under pressure to the inner
passage of shaft 55, the means for tensioning the flange 64
revolving bodily with the pulley.
It may be noted that as a counterpart of these various advantageous
features the device may be attended by the following
inconveniences:
The air pressure in the pulley control system adds itself to the
force of return spring 67 exerting a pressure against the pulley
flange 64; this pressure is uselessly important when the minimum
relative distance of pulley flanges 56 and 64 is minimum (i.e. when
the belt engages the largest pulley diameter and the reaction
torque of the supercharger attains its lowest value and can entail
a premature wear and tear of belt 15);
The belt-tensioning spring blade 60 is abnormally sensitive to the
vertical accelerations "awakening" the inertia of this pulley.
Therefore, some type of damping device is necessary for avoiding
detrimental variations in the belt tension, belt slippage and,
consequently, a premature belt wear and tear.
According to another modified form of embodiment of the present
invention, which permits eliminating the two inconvenience set
forth hereinabove, the transmission ratio variation is again
obtained by using the action of compressed regulation air against a
single pulley 56, 64 having its movable flange 64 urged by a spring
67 towards the companion flange 56 while the pulley shaft 55 is
connected through a universal joint and supported as close as
possible to the pulley, and on the opposite side thereof, by a
single ball bearing 73 (see FIGS. 9 and 10). However, in this case
a fluid-actuated cylinder is so pivotally mounted between the
engine and the bearing that the movable member or piston of this
cylinder causes the distance between centers of these pulleys, and
therefore their transmission ratio, to vary as a function of the
regulation air pressure.
Advantageously, the fluid-actuated cylinder will be of the
compensated type wherein the working chamber is supplied with
regulation air, the movable member of this cylinder being urged by
spring means acting in a direction opposite to of said regulation
air. In this case, the use of a helical compression spring as a
substitute for the spring blade and its light bracket permits
constructing a lighter assembly mounted directly through pivot
means on the engine case or block.
A pneumatic damper may be interposed between the fixed and movable
members of the fluid-actuated cylinder in order to damp out the
movements of the movable member.
Finally, the use of rolling diaphragms will eliminate any problem
concerning the fluid tightness in the working chamber of the fluid
actuated cylinder.
As illustrated in FIGS. 9 and 10 showing a typical form of
embodiment of this alternate construction, the pulley comprises a
fixed flange 56 rigid with shaft 55 revolving in the single bearing
73 pivotally mounted by means of trunnions 79, and an axially
movable flange 64 urged by a return spring 67 against its companion
flange 56 so as to clamp the V-belt 15.
The trunnions 79 of the swiveling bearing 73 are solid with the
piston rod 86 to which the upper piston 92 is welded; the upper
rolling diaphragm 93 is adapted to roll on this piston 92 during
the downward movement of this piston within the upper cylinder
91.
This rolling diaphragm 93 is clamped in a fluidtight manner against
the bottom of piston 92 by means of a washer 74 and a nut screwed
on the lower end of rod 86 and adapted to assemble the lower piston
78, the lower diaphragm 77, the washer 76, the distance-piece 75,
the washer 74 and the aforesaid diaphragm 93 by tightening against
said piston 92. The outer edge of diaphragm 93 is clamped in a
fluidtight manner between the lower flange of cylinder 91 and the
upper flange of the intermediate cylinder 94. The outer edge of the
lower diaphragm 77 is clamped also in a fluidtight manner between
the connecting flanges of the intermediate cylinder 94 and of the
lower cylinder 88.
The fluidtight chamber bounded by diaphragms 77 and 93, their
clamping washers 74 and 76, distance-piece 75 and intermediate
casing 94 is supplied with regulation air pressure through a
flexible pipe connected to port 80. This pressure compensated by
spring 82 is used for adjusting the vertical position of the
pistons, rod 86 and pump 10, by varying the distance between the
centers of this pulley and of the fixed driving pulley, and
therefore the transmission ratio between these pulleys.
The spring 82 centered with respect of the bottom of the lower
piston 78 by a washer 81 is centered at its opposite end by a
shallow neck secured directly to the case 87. By thus causing the
spring 82 to react directly against the case 87 the trunnions or
pivot pins 85 are relieved from undue stress and subjected only to
the forces produced by the regulation air.
The chamber 90 between the lower cylinder 88 and the piston 78
which is bounded at its ends by the diaphragm 77 and the piston
packing 84, communicates with the free atmosphere through a gauged
orifice 83 and acts as a dashpot or pneumatic damper for damping
out the oscillations resulting from the piston movements.
The assembly, except the spring 82, is pivotally supported by said
trunnions 85 bearing on brackets 89 rigid with the engine case
87.
This invention is also concerned, as an alternate solution to the
problem of, and a substitute for the coupling and step up
transmission 23, 24, 37, 39 to 41, and 37, 39, 49 and 50
illustrated in FIGS. 2 and 4 respectively, with a device adapted to
climinate or at least reduce internal leakages in the pump 10,
which is illustrated very diagrammatically in FIGS. 11 and 12.
Referring first to FIG. 11 it will be seen that a
compression-ignition engine 1 is supercharged by means of a
turbosupercharger 52 and a Rootes pump 10 driven at a variable
speed by the pulley 95, belt 15 and pulley 96.
The heat exchange device of the corrector is not shown.
The volumetric supercharger is driven from the engine crankshaft by
the variable-speed transmission causing this supercharger to
generate an output-volume now greater, now smaller than the cubic
capacity of the engine cylinders.
The variable speed drive is not illustrated. This device may be of
any suitable and known type, for example a V-belt variator, or a
hydraulic pump and hydraulic motor assembly of the barrel-piston
type, etc.
Conventionally, the engine is equipped with a starter motor 97, a
fuel feed pump 98 and a fuel injection pump 99. In the pipe or duct
6 connecting the turbosupercharged 52 to the pump 10 a fuel
injection is produced at 100, i.e. slightly upstream of the
volumetric pump 10.
The fuel is fed via a pipeline 101 and the output is adjusted by
properly selecting the orifice diameter of the fuel jet 102 as well
as the pressure at the outlet of the feed pump 98 (FIGS. 11 and
12).
Under normal operating conditions this output is cut off by the
electromagnet valve 103 closed when energizing current is fed to
its winding. This current is supplied through an electric conductor
104 connected to the starter motor supply conductor 106 via a
switch 107 responsive to a thermostatic control device 108. This
thermostatic control device may consist preferably of a bellows
capsule immersed in the engine cooling liquid flowing through the
duct 109, as shown.
This device operates as follows:
Assuming that the engine is inoperative and the water temperature
rather low, contact 107 is closed. When the switch 106 controlling
the energization of starter motor 97 is closed the electromagnet
valve 103 opens as the engine performs its first revolutions. The
fuel pump 98 delivers a pressure depending on the force of its
spring, and a fuel output is directed through the jet 102. Thus,
the pump 10 is driven from the engine with the maximum transmission
ratio but at a very low speed.
The fuel mixed with air penetrated into the pump 10 and wets the
inner walls of its stator as well as the rotor surfaces. The
clearences between stator and rotors and between rotors, which are
normally of the order of 0.004 inches, practically cancel each
other and the volumetric ratio between the pump 10 and engine 1
creates the expected overpressure. The final pressure and
temperature in the engine combustion chambers become sufficient for
causing the first combustion, inasmuch as the latter is promoted by
the slight vapor caused by this additional fuel injection.
Of course, the size of the orifice of jet 102 is selected after
proper tests and also as a function of the temperature at which the
switch 107 is to be operated.
* * * * *