Device for regulating the air supply of an internal combustion engine

In a device for regulating the air supply of an internal combustion engine supercharged by a turbo-compressor unit driven in rotation by the engine's exhaust, the intake of the rotating compressor is controlled by an intake regulation (or gating) system capable of reducing the compressive effect of the rotor of the compressor. Control elements of said regulation (or gating) system are connected with the accelerator linkage so as to close the regulation (or gating) system and reduce the compressive effect to the maximum degree when the accelerator moves toward the idling position of the engine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for regulating the air supply of 
an internal combustion engine supercharged by a turbo-compressor unit 
rotatably driven by the engine's exhaust. The invention applies 
particularly to controlled ignition engines running on gasoline or other 
vaporizable fuel for which the intake of air at the entrance to the 
combustion chambers of the engine can be choked by a regulator element, 
such as one or more butterfly valves, controlled by an accelerator linkage 
located downstream from the compressor. 
2. Description of the Prior Art 
One drawback of this arrangement appears upon acceleration from idle. The 
turbo-compressor rotor is turning at a relatively low speed during idle. 
To regain speed requires several seconds of acceleration under the effect 
of the still limited exhaust flow of the engine. At the instant the 
turbo-compressor rotor first begins to pick up speed, the compressor 
rotor, which is turning at low speed, acts to create a pressure loss in 
the engine's air supply circuit, instead of delivering a pressure boost. 
This further reduces the flow of air taken in by the accelerating engine, 
even though the engine's air supply butterfly valve is fully open. It is 
only after a considerable increase in the speed of the turbine that the 
air supply pressure of the engine will exceed the atmospheric pressure and 
thus create an appreciable increase in the flow of exhaust gas, enabling 
rapid acceleration of the turbo-compressor rotor to its maximal speed and 
assuring a clear pressure boost to the engine. 
SUMMARY OF THE INVENTION 
One of the objects of the present invention is to reduce the response time 
in the acceleration of controlled ignition engines supercharged by 
turbo-compressor when their performance in changing speeds, and especially 
in reacceleration, is compared to the performance of similar 
non-turbocharged engines. 
For this purpose, the intake of the rotating compressor is controlled by a 
regulator (or gating) system capable of reducing the compressive effect of 
the compressor rotor, with control of said regulator system being 
connected with the control of the accelerator linkage. The regulator 
system operates to reduce the compressive effect of the compressor to the 
maximum degree possible when the accelerator moves toward the idle 
position of the engine so as to cut the power consumed at this point by 
the compressor and to keep the rotor of the turbine-compressor unit at a 
high speed in order to reduce the time lag in the resumption of speed of 
said rotor when the engine regains speed, while allowing for a quick cut 
in the power of the engine by the intake regulator element of the engine. 
The regulation (or gating) system consists generally of a series of blades 
disposed within the annular supply passage of the compressor and arranged 
to pivot about an axis mechanically connected to the accelerator linkage. 
The blades can pivot between a position aligned in the direction of the 
radial air intake flow at full acceleration of the engine and a position 
which sets the air at the compressor intake into rotation in the direction 
which will reduce the delivery pressure of the compressor. 
According to an embodiment of the invention, control of the regulator 
system is connected with the accelerator linkage by a mechanical linkage 
that senses the movement of the accelerator and an element for sensing the 
air pressure at the engine intake, downstream from the compressor. The 
element for sensing the air pressure prevents full opening of the 
regulator system as long as said air intake pressure into the engine is 
lower than a pre-set value corresponding to significant pressure boost. 
The mechanical linkage may comprise a cylinder barrel integral with an 
accelerator link and containing a piston connected mechanically to the 
regulator system control. The piston is controlled, on the one hand and in 
the open direction of the regulator system, by the air intake pressure at 
the entrance to the engine at a point downstream from the butterfly valves 
and, on the other hand, by the reactive force of a return spring and the 
atmospheric pressure or to the pressure at the compressor intake. 
Accordingly, the return spring will limit the opening of the regulator (or 
gating) system in the absence of a significant pressure boost at the 
engine intake and increasing pressure boosts at the engine intake will 
cause the regulator (or gating) system to open progressively until the 
blades are fully open. 
According to one method of controlling the sytem of the invention, with the 
engine at idle the air choking element controlled by the accelerator 
linkage is set to shut the air intake to the engine only partially, while 
the accelerator/regulator (gating) system control connection is set to 
induce a substantial closing of the gating so as to enable the compressor 
rotor to turn at relatively high speed while the engine is at idle, a time 
when the intake pressure-loss across the compressor usually occurs. 
According to another aspect of controlling the air regulation system of the 
invention, with the engine at idle, the connection of the accelerator 
linkage with the regulator system (consisting of a series of blades 
disposed in the annular supply passage of the compressor) is set up to 
produce a powerful rotation of air at the compressor intake in the 
direction of the rotational drive of the rotor of said compressor so as to 
drive in rotation, at least partially, the compressor rotor, and thereby 
to enable this rotor to turn more quickly while the engine is at idle, 
while at the same time forming together with the regulator element an 
intake pressure loss capable of choking the engine's air intake consistent 
with operation at idle or at low speeds. 
The air supply regulation means of the invention are particularly 
applicable to controlled ignition engines, which present difficulties in 
the adaptation of the supercharging turbo-compressor to the intake speed, 
with choking of the air flow at the intake of the engine being provided 
either directly, as with fuel injection, or through a carburetor. With 
diesel engines, air suction is restricted only by the pressure losses in 
the intake circuit, which is always wide open, and the engine always has a 
significant exhaust pressure available to it, thus ensuring a high minimum 
speed of rotation of the turbo-compressor rotor. By contrast, with 
controlled ignition engines, the intake pressure may, through choking at 
the carburetor, become very low (with values lower than 0.2 bars) and 
yield post-expansion exhaust pressures which are barely greater than the 
atmospheric pressure (although combustion pressure is nevertheless much 
greater than the atmospheric pressure in order to turn the engine over). 
In this case, the pressure will no longer even spin the rotor of the 
turbo-compressor. 
The device of the invention enables the turbo rotor to rotate at relatively 
high speed even with the engine at idle by increasing the exhaust pressure 
and using a portion of the suction power of the engine to cause the rotor 
to act as turbine under the effect of the engine's suction-induced low 
pressure. Such a system has the risk of increasing fuel consumption 
slightly at idle, but it greatly improves the engine's smoothness and 
efficiency in operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to FIG. 1, an engine 1 with three cylinders 2, 3 and 4, is 
equipped with an air turbocharging unit consisting of a centrifugal 
turbine 6 of which the rotor 5, housed within a volute housing, is placed 
in the path of the exhaust gas from turbine intake pipe 8 connected to 
engine exhaust pipes 9 which are in turn connected directly to the exhaust 
valve outlets of the engine. The intake of turbine 6 is tangential and the 
centripetal flow of the exhaust gas leads to an axial outlet connected to 
an exhaust pipe 10. Turbine rotor 5 is connected by a shaft 11, journalled 
on bearing 12 (generally lubricated by the engine's oil pressure), to a 
rotor 7 of a compressor 13 housed in a volute housing 14 and connected by 
an intake pipe 15 to air intake in the form of a regulating distributor 
32. 
Compressor rotor 7, rotatably driven by turbine rotor 5, takes in the 
engine combustion air axially and compresses it radially in a centrifugal 
flow toward an intake collector 16 which leads into the intake valves of 
cylinders 2 through 4, after cooling in heat exchanger 16a. 
In order to limit the intake pressure within collector 16 and the 
combustion chambers of cylinders 2-4 and, consequently, the maximum 
combustion pressure exerted on the pistons of the engine, in the case of a 
diesel engine, and alternatively, the risk of knock in a controlled 
ignition engine, the circuit of turbine 6 is equipped with a bypass 
circuit consisting of a discharge valve 17 lodged within conical seat 18. 
By moving away from seat 18, valve 17 opens an annular passage which 
enables exhaust gas to be discharged directly from exhaust pipes 9 into a 
discharge pipe 9a, thus short-circuiting the blades of rotor 5 of turbine 
6. The flow of exhaust gas across turbine 6 is thus reduced, considerably 
diminishing the speed of rotation of rotors 5 and 7 and, consequently, the 
delivery pressure of compressor 13 into intake collector 16. 
The air pressure within intake collector 16 may be regulated with the aid 
of a regulator element 19 comprising two chambers 20 and 21 separated by a 
piston 22, generally of the membrane type in order to obtain a perfect 
seal with low operating hysteresis. Chamber 21 is connected to intake 
collector 16 downstream from compressor 13 and the pressure of the 
supercharged air prevailing in chamber 21 acts upon piston 22, connected 
by rod 23 to discharge valve 17, in opposition to a spiral spring 24 
lodged within chamber 20. When the pressure in collector 16 downstream 
from compressor 13 and acting upon piston 22 exceeds the calibration of 
spring 24, valve 17 moves away from its seat 18 and a flow of gas is 
released directly into pipe 9a, which reduces the speed of the rotors of 
turbine 5 and compressor 7 and immediately stabilizes the supercharging 
pressure within intake collector 16. The chamber 20 is in contact with the 
atmosphere, or the intake collector of compressor 13 through a pipe 20a in 
which case the pressure in chambers 20 can be brought down to a pressure 
lower than the atmospheric pressure. 
Additional air intake regulation elements are provided according to the 
invention to ensure (when engine 1 is of the controlled ignition type) 
maximum speed of rotation of turbo-compressor rotor elements 5, 11, 7 when 
the engine is running at idle or at low speeds. 
These additional elements comprise a butterfly valve 25 at the mouth of 
each intake pipe 26 of cylinders 2-4 of engine 1. These butterfly valves 
are activated by a linkage 27 connected by a set of levers 28 to an 
automatic or manual control such as an accelerator pedal linkage 29. An 
adjustable stop 30 is inserted in linkage 27 to prevent butterfly valves 
25 from closing completely. An elastic device, such as a spring cup 31 
inserted in linkage 27, enables levers 28 to continue their rotation when 
valves 25 are stopped partially open or closed against stop 30. 
According to the invention, air drawn in by compressor 13 crosses a 
pre-rotation distributor 32, the movable blades 33 of which are disposed 
within an annular intake passage 34 and rotate about axes 35. Axes 35 of 
distributor 32 are connected by a regulator (or gating) ring 36 controlled 
by a mechanical-pneumatic activator cylinder 37. The regulator ring 36 is 
connected as by gearing to the axes 35 such that rotation of the ring 36 
causes the blades 33 to pivot from an open radial position which permits 
radial inflow of air into passage 34 to an oblique partially closed 
position which causes the inflow of air into passage 34 to rotate. The 
barrel 38 of cylinder 37 is mechanically connected through linkage 39 to 
levers 28 for movement with levers 28, while an inner chamber 40 of 
cylinder 38, occupied by a piston 41, is connected through tube 42 to one 
of intake pipes 26 downstream from a corresponding butterfly valve 25. 
Piston 41 is connected by its rod 43 to regulator (or gating) ring 36 and 
is drawn toward the bottom of cylinder barrel 37 by a return spring 44. 
The operation of the regulation device of the invention will now be 
explained. 
When engine 1 is under full load, butterfly valves 25 at the entrance to 
the engine are wide open, as are blades 33, which are pushed into open 
position both by the movement of the linkage 39 and by the supercharging 
pressure brought through tube 42 into chamber 40 of cylinder 37, which 
pressure acts upon piston 41 against spring 44 to move the rod 43 out of 
the cylinder. 
The supercharging pressure is limited to a maximum value possible without 
causing knocking in the engine 1. The pressure is limited by valve 17, 
which opens when the pressure in collector 16 exceeds the calibration 
pressure of spring 24. 
When the driver of the vehicle equipped with engine 1 suddenly raises his 
foot from the accelerator to close the linkage 29, butterfly valves 25 are 
suddenly pushed into a partially closed position, the pressure in tube 42 
drops suddenly, and cylinder 37 draws the rod 43 inward and the regulator 
(or gating) ring 36 toward its closed position, thereby folding blades 33 
very sharply and setting the intake air into rotation about the axis of 
compressor rotor 7 and in the direction of rotation of said compressor 
rotor, which then functions partially as a turbine under the suction 
effect of engine 1. 
The pressure loss caused by the operation of compressor 13 as a turbine 
causes the flow of air at the intake of engine 1 to drop rapidly, causing 
engine compression drag and possibly a slow-down to idling speed. The 
speed of rotor elements 5, 11 and 7 of the turbo-compressor diminishes in 
a limited way, particularly when the engine compression is creating a drag 
effect on the vehicle, and in any case the drop in turbo rotor speed is 
much less rapid than if the compressor intake were not subjected to 
regulation (gating) by the folded blades. 
The regulator (gating) of distributor 32 closes as the pressure in chamber 
40 of cylinder 38 drops, with the lowest pressure being obtained when the 
engine compression is exerting drag on the vehicle. The rotors of 
compressor 7 and turbine 5 then operate to choke the intake and exhaust 
respectively in order to obtain the maximum retention torque over the 
engine. 
The most spectacular results of the device of the invention are obtained 
upon reacceleration of the engine, e.g., in coming out of a turn after a 
phase in which the engine has exerted drag on the vehicle. The rotor of 
the turbo-compressor, driven by the suction of the motor acting upon 
compressor rotor 7 and the exhaust gas acting upon turbine rotor 5, is 
still turning at relatively high speed. Upon the resumption of 
acceleration, butterfly valves 25 at the mouth of the intake pipes are 
opened wide but the pressure boost in collector 16 does not exist. 
Cylinder 37, by mechanical control through linkage 39 alone, then causes a 
slight opening of blades 33 towards the radial direction. This is 
represented in zone 45 of the graph in FIG. 2 in which P is the pressure 
sensed by chamber 40 and .alpha. is the blade angle, with 90.degree. being 
a fully open position. At this moment, rotor 7 of compressor 13 is 
slightly braked by the flow of air drawn through the compressor by the 
engine, while turbine rotor 5 is accelerated by the exhaust gas already 
being delivered at a high rate. Turbo rotor 5, 11, 7 accelerates very 
rapidly and remains at a high speed while, under the effect of the 
pressure rise in collector 16 and in chamber 40 of cylinder 37, blades 33 
move progressively into zone 46 of FIG. 2, i.e., into radial position to 
allow for full compression pressure at compressor 13. The increase in 
engine power is much more rapid than with systems providing direct air 
supply to the compressor without the intake air being set into rotation 
and the power consumed at the compressor before the effective rise in 
pressure in the intake collector is reduced. This property is all the more 
valuable since the presence of heat exchanger 16a, acting as a cooling 
unit, increases the volume of air stored between compressor 13 and the 
cylinder inlet ports, as well as increasing the pressure loss between 
compressor 13 and cylinders 2-4. It must also be noted that heat exchanger 
16a, particularly an air/water exchanger, may also serve to reheat air 
admitted to the cylinders after said air has undergone a marked drop in 
pressure and temperature due to expansion through compressor rotor 7 
(operating as a turbine). In such a situation, turbine rotor 5 may operate 
as an exhaust gas removal pump driven by compressor rotor 7 playing the 
role of a turbine. 
When the engine is running at steady, middle-range power, butterfly valves 
25 of the engine are set in nearly fully open position, but the blades 33 
of distributor 32 do not move into a fully open radial position, since the 
linkage 39 can not yet pull them into such a position (which is reserved 
for occasions in which the engine is at full power). The slight rotation 
of air at the intake of compressor rotor 7 enables the rotor to reach a 
speed of rotation which may be greater than its nominal speed under full 
load. This arrangement shortens the response time of the motor upon full 
acceleration, as needed, for example, when passing another vehicle. 
The power regulation device of the invention, for a controlled ignition 
engine having a turbo-compressor, provides numerous advantages over the 
prior art. Among these benefits may be cited: 
1. Better proportioning of air flow and engine power by the intake valves 
of the cylinders, resulting in increased smoothness of the engine. 
2. Reduced response time when decelerating and, especially, when 
reaccelerating, particularly from a partially open position, or from a 
position in which the engine has been exerting compression. 
3. Better opportunities for proportioning the air/gas mixture by using 
angle of opening of the cylinder intake valves as a parameter, i.e., in 
using a classic carburetor. 
4. Better control of the speed of the turbo-compressor which, in case of 
prolonged operation at idle, no longer risks stopping. 
5. Better engine-braking (drag) effect. 
The engine intake butterfly valves may be replaced by drop-gates or any 
other valve-gate regulator device. The movable blade distributor 32 may be 
replaced by any other device capable of inducing prerotation which can be 
varied as a function of opening angle, such as a grill of turbojet blades. 
The mechanical and pneumatic controls of the variable prerotation 
distributor 32 could also be replaced by other devices which take into 
account the air flow of the engine, particularly electronic means using 
the following as parameters: the speed of the engine; intake pressure, 
exhaust pressure, intake temperature, the opening angle of the engine 
intake butterfly valves and the speed of rotation of the turbo-compressor. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.