Apparatus for controlling the air supply to the intake manifold of an internal combustion engine

Apparatus for controlling the air supply to the intake manifold of an internal combustion engine having an intake system comprising a carburetor, the carburetor having a throttle, means for admitting air from the atmosphere and conducting the air to the carburetor for mixing with fuel, and conduit means for conducting the mixture of air and fuel from the carburetor to the intake manifold, the apparatus comprising auxiliary conduit means for conducting fuel--free air into the engine, the auxiliary conduit means communicating with the intake system at a point downstream of the throttle, a displaceable member associated with the auxiliary conduit means, the displaceable member being displaceable between a position in which the member blocks the access of air from the auxiliary conduit to the intake manifold and positions in which the member at least partly opens access of air from the auxiliary conduit to the intake manifold, an electromagnet associated with the displaceable member for controlling the displacement of the member, means for controlling the energization of the electromagnet, the energization controlling means including at least one switch responsive to pressure variations occurring in the intake system, and means for transmitting pressure variations from the intake system to the pressure responsive switch thereby to actuate the pressure responsive switch.

BACKGROUND OF THE INVENTION 
The invention relates to a device for controlling the air supply to the 
inlet manifold of a combustion engine at a point located downstream of the 
throttle valve of the carburetor. 
A combustion engine, particularly a gasoline engine used in a motor car 
frequently operates under conditions in which an excessive quantity of 
fuel is supplied for the required operation of the engine, which involves 
an excessively high fuel consumption and/or polution of the air. 
If, for example, the number of revolutions of the engine in accelerating 
the vehicle is raised to about 3000 rev./min. and the clutch is 
subsequently loosened for changing over to a higher gear, the throttle is 
closed and the subatmospheric pressure in the inlet branch pipe downstream 
of the throttle generally attains a value which even exceeds that at a 
standstill of the rotating engine. Then a great pressure difference is 
created across the stationary fuel supply device, which thus delivers an 
unnecessarily large quantity of fuel. A fairly large portion of this fuel 
will leave the engine without being burnt and thus contribute to 
pronounced pollution of the air or this fuel is at least partly deposited 
in the inlet manifold and is again carried along at the subsequent opening 
of the throttle and hence at an increase in the quantity of air flowing 
through the inlet manifold, the fuel thus leaving the engine again without 
being combusted. Under these and similar conditions it is desirable to 
supply additional air downstream of the throttle in order to act upon the 
pressure difference across the throttle so that on the one hand 
undesirable and unnecessary supply of fuel is avoided at the instants when 
no power is required from the engine and on the other hand the ratio of 
air and fuel flows, is acted upon to effect a reduction of the fuel 
consumption of the engine and reduce air pollution. 
According to the invention this can be achieved by providing the device 
with a closing member included in an air supply channel, the displacement 
of said member being controlled by at least one electromagnet, the 
energization of which is controlled by means of at least one switch 
responding to pressure variations occurring in the inlet system of the 
engine. 
By using at least one switch determining the energization of an 
electromagnet actuating the closing member, pressure variations occurring 
in the inlet system are prevented from directly acting upon the 
displacement of the closing member, since otherwise undesirable or 
inadequate displacements of the closing member might be involved.

FIG. 1 shows schematically the inlet manifold 1 of a gasoline engine 
provided with a carburetor 2 (shown schematically), and in a conventional 
manner a throttle 3 is arranged between the carburetor and the inlet 
manifold. The carburetor is provided with an air filter 5 of known type. 
A box 6 arranged near the engine accommodates a closing member formed by a 
housing 7 accommodating a slide 8. A compression spring 9, arranged in the 
housing 7, tends to urge the slide 8 upwards against the bottom end of a 
connecting piece 10 screwed into the top of the housing and adapted to be 
fixed in any desired position by means of a nut 11 screwed onto the outer 
side of the connecting piece 10. 
The connecting piece 10 has connected with it one end of an air hose 12, 
the other end of which is connected with the air filter 5. As an 
alternative a separate air filter may be provided on the connecting piece 
10. 
The housing 7 is furthermore provided with a connecting stud 13, the 
passage of which is shut completely or substantially completely in the 
position of the slide 8 shown in FIG. 2 and FIG. 7. The connecting stud 13 
has connected with it a hose 14, which causes the stud 13 to communicate 
with a connecting piece 15 fastened to the inlet manifold 1. 
On either side of the closing member the box contains two switches 16 and 
17. The switch 16 is shown in detail in FIG. 3 and comprises a 
substantially cylindrical housing 18 holding a piston 19. The piston 19 
has secured to it a rod 20, which is passed through a lid 21 closing the 
housing. The rod 20 is surrounded by a compression spring 22, which is 
enclosed between the lid 21 and an annular plate 23 secured to the rod 20. 
The plate 23 is adapted to reciprocate between two contact pins 24 and 25 
adjustably arranged in the lid. 
The housing 18 is furthermore provided with a connecting spout 26 for 
receiving an air hose 27 (FIG. 1), which communicates through a T-joint 28 
and an air hose 29 with the inlet system at a point located just above the 
throttle 3, when the throttle 3 is closed. the T-joint has a further air 
hose 30, which is connected in known manner with the mechanism controlling 
the pre-ignition of the engine. 
The switch 17 shown in FIG. 4 is constructed in a manner similar to switch 
16, and it comprises a housing 31 accommodating a piston 32. The piston 
has secured to it a rod 33, which is passed through a lid 34 covering the 
housing. The rod 33 is surrounded by a compression spring 35 which is 
enclosed between the lid 34 and an annular plate 36 fastened to the rod 
33. The plate 36 is adapted to reciprocate between two adjustable contacts 
37 and 38 secured to the lid 34. 
The housing 31 is furthermore provided with a connecting piece 39 for one 
end of a hose 40, the other end of which is connected with the connecting 
piece 15. 
It will furthermore be apparent from FIG. 2 that the slide 8 is surrounded 
by a coil 41, which can be energized through a bi-stable switch 42. 
At its center the slide 8 has a stepped bore 44, the portion of the bore 
having the larger diameter receiving the thickened top end 45 of a rod 46 
passed through the bore 44, the end of the rod projecting beneath the 
slide 8 being connected with a piston-like body 47, which constitutes an 
armature for an auxiliary coil 48 arranged beneath the coil 41. The 
auxiliary coil 48 can be energized through a bi-stable switch 43. 
The stroke which the armature 47 can perform with the aid of the auxiliary 
coil 48 is adjustable by means of an adjustable stop 49, which can be 
fixed in place by means of a safety nut 50. 
The system described in the foregoing operates as follows. 
If at a stationary speed the supply of additional air to the inlet manifold 
is not required, the switch 16 may be adjusted so that the plate 23 
engages the contact 25, whereas the plate 36 is just free of the contact 
38 when the engine is rotating in a standstill. When the throttle is 
slightly opened, the resulting expansion of the combustion air downstream 
of the throttle will cause the mixture to be enriched. However, at the 
opening of the throttle the subatmospheric pressure at the junction of the 
duct 29 and hence the subatmospheric pressure beneath the piston 19 in the 
housing 18 of the switch 16 will increase so that the piston 19 moves 
downwards and the plate 23 establishes a contact with the contact 24. 
Thus, current is applied to the bi-stable switch 43, which results in the 
energization of the auxiliary coil 48 so that the armature 47 and hence 
the slide 8 are moved downwards over a small distance. Thus part of the 
passage 13 is opened and air sucked in through the filter and the duct 12 
can flow through the duct 14 towards the inlet manifold so that the 
harmful effect of an excessively rich mixture is reduced. 
When the throttle is opened further and the speed of the engine increases, 
the subatmospheric pressure in the inlet manifold and hence the 
subatmospheric pressure beneath the piston 32 in the housing 31 of the 
switch 17 will gradually decrease so that the piston 32 can move upwards 
by the action of the spring 35 until the plate 36 engages the contact 37. 
When this contact is established, a pulse is applied to the bi-stale 
switch 43, which results in the suppression of the energization of the 
auxiliary coil 48 so that the slide 8 can move into its closed position. 
As a result, the supply of additional air to the inlet manifold is 
interrupted under such operational conditions of the engine as to 
guarantee a satisfactory mixing of air and fuel in a satisfactory ratio 
and a satisfactory combustion. 
When changing over to another gear or when braking the vehicle by means of 
the engine, the number of revolutions of the engine will be comparatively 
high at the instant of closing of the throttle. When the throttle is 
closed, at least initially a subatmospheric pressure will be produced in 
the inlet manifold downstream of the throttle in excess of the 
subatmospheric pressure produced in stationary operation. Owing to this 
subatmospheric pressure the piston 32 of the switch 17 will move downwards 
until the plate 36 comes into contact with the contact 38, whereas owing 
to the decrease in subatmospheric pressure beneath the piston 19 of the 
switch 16, this piston 19 has again moved upwards so that the plate 23 
engages the contact 25. The establishment of contact between the plate 23 
and the contact 25 completes the current supply to the bi-stable switch 
42, and the establishment of contact with the plate 36 and the contact 38 
produces a pulse for the bi-stable switch 42 so that the main coil 41 is 
energized and the slide 8 is withdrawn, the passage 13 being completely 
opened, as a result of which a large quantity of air can flow towards the 
inlet manifold, the subatmospheric pressure in the inlet manifold being 
thus considerably decreased, which involves also a material reduction of 
the fuel supply not required under the operational conditions concerned 
and as the case may be, said supply may even be completely stopped. 
As long as the switch 16 remains in the last-mentioned position, i.e. the 
plate 23 engaging the contact 25, the bi-stale switch 42 not receiving a 
further pulse, the coil 41 remains energized so that, if due to a decrease 
in subatmospheric pressure in the inlet branchy pipe the contact between 
the plate 36 and the contact 38 would be eliminated, the supply of 
additional air to the inlet manifold in nevertheless maintained. 
In order to prevent the engine from cutting out, for example, when braking 
the vehicle by means of the engine to a standstill, an electronic system 
(not shown) is provided, which is operative in dependence upon the speed 
of the engine, said electronic system being, for example, arranged so that 
it responds to the number of pulses of the coil per unit time and 
generates a pulse to the bi-stable switch 42, when a given minimum speed 
is attained, so that the energization of the coil 41 is obviated and the 
slide 8 is moved back into the closed position by the spring 9. 
If the throttle is re-opened after the change-over, the increase in the 
subatmospheric pressure in the housing 18 of the switch 16 will cause the 
piston 19 to move downwards so that the contact between the dish 23 and 
the contact 25 is interrupted. The current supply to the coil 41 is thus 
suppressed so that the slide 8 will again be moved into the closed 
position by the spring 9. 
In order to obtain a very poor mixture in the state of stationary operation 
without adversely affecting the engine operation under other operational 
conditions, the signal generated by the electronic system (not further 
defined) when the given minimum speed is attained, is employed not only 
for preventing the coil 41 from being energized but also for energizing 
the auxiliary coil 48 only in state of stationary operation. The part of 
the passage 13 thus opened serves as a basic opening for the other 
operational conditions in which the auxiliary coil 48 is energized, which 
means that the stop 49 is adjusted so that at the stationary speed quiet 
running of the engine is nevertheless ensured with a partly opened passage 
of the connecting stud 13 owing to the action of the auxiliary coil. In 
the case of high engine speeds, for example, of a number of revolutions of 
3500 to 4000 a minute and higher, the supply of additional air will be 
desirable in order to ensure an optimum combustion of the whole quantity 
of fuel. At these speeds a compulsory opening of the slide 8 over a given 
distance can be carried out with the aid of an electronic circuit (not 
shown) also responding to the engine speed and, for example, also being 
operative in dependence upon the number of pulses of the coil, said 
circuit supplying a current to the bi-stable switch 43 at a speed 
exceeding 3000 to 3500 rev./min., so that the auxiliary coil 48 is 
energized and the slide 8 is drawn downwards by means of the armature 47, 
the connecting stud 13 being thus again partly opened. When the speed of 
the engine drops below said number of revolutions, the current to the 
bi-stable switch and the coil 48 will again be interrupted, so that the 
slide 8 can return to its closed position. 
When, as stated above, the slide 8 has been opened over a given distance 
with the aid of the auxiliary coil 48 and the armature 47 in the case of a 
comparatively high speed, the rate of supply of additional air through the 
connecting piece 10 and the connecting stud 13 will increase at a further 
increase of speed, so that the pressure exerted on the end of the slide 8 
increases to an extent such that it can be urged downwards against the 
action of the spring 9 until in the passage the critical speed is attained 
and a state of equilibrium is established between the resultant of the 
force produced by the dynamic pressure on the end of the slide 8 and the 
force of the spring 9. 
In certain cases it may be desirable to open the slide 8 still further for 
admitting a larger quantity of additional air. This may be done by means 
of the construction shown in FIG. 5. In this figure those parts which 
correspond to parts of the preceding embodiment are designated by the same 
reference numerals. In this embodiment the armature 47 is freely slidably 
along the rod 46 and the lower end of the rod 46 passed through the 
armature 47 is provided with a piston-like body 51 forming a further 
armature, which is adapted to cooperate with a further auxiliary coil 52, 
arranged beneath the auxiliary coil 43. 
The armature 47 is held at a distance from the armature 51 by means of a 
sleeve 53 surrounding the rod. 
If the armature 43 is initially energized first, resulting in a given 
displacement of the slide 8 and the slide 8 being subsequently urged 
further down against the action of the spring 9, as stated above, the coil 
52 can be energized, when a given speed is exceeded, so that the slide 8 
is drawn still further downwards. 
As a matter of course it is possible, particularly with engines having a 
larger cylinder capacity to provide several auxiliary coils of the kind 
set forth, which are stepwise energized upwards of a given speed during 
the further increase in speed in order to provide a gradual progression of 
the additional air supply. 
FIG. 8 illustrates, in simplified form, the electrical system of the 
invention, as above disclosed. In this arrangement, the bi-stable switches 
42 and 43 may comprise conventional flip-flop circuits, with or without 
driving amplifiers as necessary in accordance with conventional practice. 
The outputs of these flip-flop circuits are connected to energizer coils 
41 and 48, respectively. 
The dishes or movable contacts 23 and 36 of the switches 16 and 17, 
respectively are returned to a positive supply. The contact 25 is 
connected to provide operating potential for the flip-flop 42, while the 
fixed contact 24 is connected to set the flip-flop 43. In the following 
paragraphs, the term "set" and "reset," refer to the triggering of the 
flip-flops into states such that their outputs connected to the respective 
coils 41 and 48 result in the energization and de-energization, 
respectively of the coils. The setting or resetting may, for example, be 
effective upon a transistion of determined polarity applied to their 
respective input terminals, in accordance with conventional practice. 
The contact 37 of the switch 17 is connected to a rreset terminal of the 
flip-flop 43, while a fixed contact 38 of this switch is connected to the 
set terminal of the flip-flop 42. 
In order to obtain triggering voltages for the flip-flops that are 
responsive to the speeds of the engine, conventional tachometer circuits 
may be employed. These tachometers may be coupled by conventional means to 
the engine, so that the necessary pulse output or voltage transition is 
effected at the conditions above described. For example, a tachometer 
circuit 80, providing a pulse or voltage transistion at a determined 
minimum speed, is connected to a reset terminal of the flip-flop 42, and 
to a set terminal of the flip-flop 43. A further tachometer 81, which 
provides a pulse or voltage transistion at a determined maximum speed is 
connected to a set terminal of the flip-flop 43. As discussed above, for 
example, the output of a tachometer may be set to occur speeds of the 
engine in excess of 3,500 rpm. 
A further possibility of obtaining a gradual enlargement of the passage for 
the additional air supply to the inlet branch pipe at high speeds is 
illustrated in FIG. 6. The parts corresponding with those of the preceding 
embodiments are denoted by the same reference numerals. In this embodiment 
the armature 47 is arranged in a sleeve 54 surrounding said armature and 
being surrounded by the coil 43 (not shown). The lower end of the sleeve 
54 encloses the top end of a further sleeve 55, the lower end of which is 
arranged in a housing 56. The top end of the sleeve 55 accomodates a 
piston-like body 57, which constitutes a stop cooperating with the 
armature 47. Through a central opening in the piston-like body 57 is 
passed a rod 58, the thickened head of which is slipped into a recess of 
the piston-like body 57 so that the piston-like body 57 cannot slip off 
the rod in upward direction and can hold in upward direction the 
piston-like body 47 at a predetermined distance from the piston-like body 
57. The rod 58 can move over a given distance without taking along the 
piston 57. The lower end of the rod 58 is provided with a piston-like body 
59. Between the piston-like body 59 and the piston-like body 57 the rod 58 
is surrounded by a compression spring 60. The sleeve 55 is provided at the 
top with an inwardly projecting collar 61, which limits the upward 
movement of the piston-like body 57. 
Between the piston-like body 59 and a shoulder formed in the sleeve 55 is 
arranged a compression spring 62. 
Beneath the piston-like body 59 is arranged a compression spring 63, the 
lower end of which is in contact with a set bolt 64 screwed into the 
housing 56 and adapted to be fixed in place with respect to the housing 56 
with the aid of a safety nut 65. Obviously the tension of the springs can 
be adjusted by turning the set bolt 64. 
With the space formed between the piston-like bodies 57 and 59 in the 
sleeve 55 communicates a connecting stud 66, which further communicates 
with the inlet branch pipe of the engine through the hose 40 and the 
connecting piece 15. 
The space beneath the piston 59 in the housing 56 is, through a bore 67 in 
the housing, in open communication with the atmosphere. 
Normally, under operational conditions under which a high atmospheric 
pressure prevails in the inlet branch pipe downstream of the throttle, the 
thickened head of the rod 58 will hold the piston-like body (armature) 47 
at a distance from the piston-like body 57, which distance diminishes 
according as the size of the gap opened by the slide 8 increases 
progressively after the energization of the auxiliary coil 48 in the range 
limited by the adjustable contact 24 of switch 16 and the adjustable 
contact 37 of switch 17. 
Under conditions of comparatively high subatmospheric pressures, i.e. in 
the ranges in which the mixture is enriched with a slightly opened 
throttle and a great expansion of the combustion air directly after the 
throtle, the piston-like body 57 will limit a downward movement of the 
armature 47 in the same manner as the adjustable stop 49 of the preceding 
embodiments. 
The setting of the various springs may then be chosen so that a decrease of 
the pressure in the space between the piston-like bodies 57 and 59 i.e. at 
an increase in speed and in excess of a given number of revolutions, when 
the auxiliary coil is energized, the piston-like body 59 is gradually 
urged downwards by the spring 62 against the force of the spring 63, the 
stop 57 for the armature 47 being thus gradually moved downwards, so that 
this armature and hence the slide 8 can also move gradually further 
downwards. The more the subatmospheric pressure in the inlet branch pipe 
decreases, the larger the distance over which the slide 8 can be displaced 
and the larger will be the passage opened for the additional air supply to 
the inlet manifold.