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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secondary air controlling apparatus to
be used to clean the exhaust gases of internal combustion engines for
vehicles.
2. Description of the Prior Art
As a way of cleaning the exhaust gases of engines for vehicles, there is
known an air injection system wherein secondary air is fed into the
exhaust passsage to burn and decompose the unburnt harmful component in
the exhaust gases. In this cleaning system, if there is a large amount of
the unburnt harmful component, when the secondary air is fed with
sufficient oxygen, an extreme after-burning will occur. Such after-burning
is liable to melt and frequently damage the cleaning system and
attachments thereto, such as a catalyst holding member.
Particularly, during deceleration, since the opening angle of the throttle
valve of the carburetor is small, less air-fuel mixture is sucked in.
Also, the pressure in the intake pipe is lowered, and the liquid fuel on
the intake pipe wall is gasified. Therefore, a rich mixture is sucked into
the cylinder, and the unburnt harmful component in the exhaust gases
increases. This condition results in the after-burning which is
undesirable to the cleaning system as described above. Under such
conditions, if the secondary air is interrupted, the after-burning can be
prevented with the feeding of the rich mixture. Consequently, the unburnt
harmful component will be discharged out of the exhaust system without
cleaning.
Therefore, during deceleration, it is desirable, on the one hand, to
interrupt the feeding of secondary air into the exhaust system to prevent
the extreme after-burning and on the other hand, to introduce secondary
air into the intake passage to dilute the rich mixture in the intake pipe
and improve the combustion within the combustion chamber. The feeding of
secondary air into the intake pipe must be made only for an initial period
of the deceleration, because if secondary air is continuously provided,
the mixture will become too lean. The feeding of secondary air into the
exhaust system should be resumed after the initial period. However, this
system requires many valves and complicated structure to make the
respective operations, and is not adapted for practical use. This problem
is solved by the present invention.
Further, when this kind of cleaning system is provided, just after the
ignition key is switched off, the engine still rotates for a little while
due to its momentum, and the air-fuel mixture sucked into the combustion
chamber under such condition is not burnt, but rather is discharged as it
is into the exhaust passage. If secondary air is fed into the exhaust
passage through a reed valve with a negative pressure part of exhaust
pulsation, the unburnt harmful component will combine with sufficient
oxygen and explosively burn in the cleaning system remaining at a high
temperature, an extreme after-burning will occur, and the exhaust cleaning
and exhaust system will be damaged. Therefore, when the engine is turned
off, it is also desirable to interrupt the feeding of secondary air into
the exhaust passage.
As a way of preventing the after-burning just after the ignition key is
switched off, there is a known method wherein, just after the ignition key
is turned off, secondary air is introduced downstream of the throttle
valve to suppress the rise of the negative suction pressure, to regulate
the fuel sucked in from the carburetor, and to prevent the unburnt mixture
from being discharged into the exhaust passage. However, in this method,
the intake passage always communicates with the atmosphere through the
secondary air introducing passage when the engine is off; the liquid fuel
on the inner wall of the intake passage evaporates and leaks out to the
atmosphere. This is undesirable from the viewpoint of air pollution, and
is another problem solved by the present invention.
The present invention solves the above-mentioned various problems in
systems for cleaning exhaust gases with secondary air.
SUMMARY OF THE INVENTION
The present invention provides a secondary air controlling apparatus for an
internal combustion engine, including: a first chamber communicating with
the downstream side of a throttle valve in an intake passage of the
engine; a second chamber communicating with the first chamber through a
first passage and with the atmosphere; a third chamber communicating with
the second chamber through a second passage and with an exhaust passage
through a check valve which opens in response to a negative pressure part
of a pulsating pressure in the exhaust passage; valve means provided
within the second chamber and moved to selectively open and close the
first and second passages; means operated by a negative pressure, and
arranged between a first negative pressure chamber and a second negative
pressure chamber; the valve means being connected with the means operated
by negative pressure of the intake passage; the first negative pressure
chamber being in communication with the intake passage downstream of the
throttle valve; the second negative pressure chamber being connected, in
parallel with a main pipe line disposed between the first negative
pressure chamber and the intake passage downstream of the throttle valve,
through a parallelly-arranged check valve and orifice, and the valve means
being moved in response to the difference in negative pressure between the
first negative pressure chamber and the second negative pressure chamber.
An object of the invention is to provide a secondary air controlling
apparatus wherein, at the time of the engine brake deceleration of a
vehicle, a negative pressure in the intake pipe is detected, and the
feeding of secondary air into the exhaust pipe is interrupted to prevent
after-burning in the cleaning system for the exhaust gases; while
secondary air is supplied into the intake passage to dilute the rich
mixture, thereby suppressing the emission of unburnt harmful components.
The invention provides a secondary air controlling apparatus including a
valve operated by the negative pressure in the intake pipe causing
secondary air to enter the suction pipe by the negative pressure
fluctuation at the time of the deceleration with engine braking and, at
the same time, the feeding of secondary air into the exhaust pipe will be
interrupted by the same valve.
Another object is to provide controlling apparatus wherein, because the
negative suction pressure is utilized, the detection of the loaded state
at the time of deceleration with engine braking is simplified and
positively attained by simple structure at minimum cost.
The invention also provides a secondary air controlling apparatus wherein a
delay circuit, including a check valve, communicates with means for moving
the valve operated by the negative pressure in order to control secondary
air only for a predetermined time, thereby positively controlling
secondary air for a required interval of time.
A further object is to provide a secondary air controlling apparatus
wherein, just after the ignition key is switched off, secondary air is fed
into the intake passage to suppress the outflow of the unburnt harmful
components into the exhaust passage due to engine momentum, to prevent
after-burning, to protect the exhaust system and cleaning device and, at
the same time, secondary air is fed into the intake passage only for a
certain period to prevent evaporated fuel from leaking out to the
atmosphere.
Concretely, the apparatus is provided with: a solenoid valve, opened by
turning off the ignition, and arranged between the above-mentioned
negative pressure operated valve and the intake passage downstream of the
throttle valve, which is a negative pressure source; and a negative
pressure reservoir controlling the negative pressure accumulation by means
of a check valve and orifice. The valve is opened by the negative pressure
in the negative pressure reservoir in response to the switching off of the
ignition, to place the intake passage in communication with the atmosphere
to supply secondary air. The negative pressure in the reservoir may be
gradually reduced by the orifice adjacent to the reservoir and, after the
lapse of a certain period, the valve may be closed to seal the intake
passage from the atmosphere.
Thus, there is obtained a secondary air controlling apparatus wherein, when
the engine stops, secondary air is fed into the intake passage positively
and effectively only for a certain period by using, for instance, a delay
valve. Moreover, such operation is attained by a simple and reliable
structure with minimum cost.
A preferred embodiment of the present invention is explained in detail in
the following with reference to the accompanying drawings so that further
objects and advantages may be made apparent.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a system circuit diagram of the present invention, showing the
device partly in section.
FIG. 2 is an enlarged, vertically-sectioned, view showing a negative
pressure operation unit.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 is an explanatory view wherein the illustrated embodiment provides
for drawing in secondary air in response to the negative pulsating
pressure in the exhaust passage. It may also provide for feeding secondary
air by means of an air pump.
An intake port of the combustion chamber of an engine 1 is connected to an
intake passage 4 by way of a carburetor 3 and an intake pipe 2. The
upstream side of carburetor 3 is connected to an air cleaner 5. A throttle
valve 6 is provided downstream of the venturi tube of carburetor 3. A
negative pressure piston 7 for controlling the opening of the venturi tube
is provided in the venturi tube. The exhaust port of engine 1 is connected
to an exhaust pipe 8, which in turn is connected to a muffler 10 through
an exhaust gas cleaning device 9, such as a catalytic converter.
A secondary air inlet 11 is provided near the exhaust port of engine 1 in
exhaust pipe 8, and is connected to a reed valve 13 through a pipe line
12.
A negative pressure switched valve 20 is operated by the negative suction
pressure. A first chamber A, second chamber B, and third chamber C are
provided in the longitudinal direction (vertical direction) or vertically
in the drawing within a body 21 of valve 20. The chambers are separated by
partition walls 22 and 24 provided with passages 23 and 25, respectively,
forming valve holes.
Chamber A is provided with an opening 26 connected through a pipe line 27
to a secondary air inlet 14 opening into suction pipe 2. Chamber A is thus
in communication with the downstream side of throttle valve 6.
Chamber B is in communication with the atmosphere through an opening 28 and
an air filter 29.
Chamber C is provided with an opening 30 which is connected through a pipe
line 31 to inlet 11 through valve 13 and pipe line 12.
A negative pressure chamber 33 is formed within a case 34 above a partition
wall 32 above chamber A, and is divided into a first negative pressure
chamber D and a second negative pressure chamber E by a diaphragm 35
provided in the middle of case 34. A valve stem 36 is secured at its upper
end to the center part of diaphragm 35, and vertically passes through a
stem guide 38 provided in a hole 37 of wall 32. Stem 36 is provided at its
lower end with a valve body 39 normally shielding the lower side of
passage 23. A spring 40 is compressed and disposed between the lower
surface of diaphragm 35 and wall 32 to resiliently press stem 36 through
diaphragm 35 toward the closing position of body 39.
Chamber D is connected through an opening 41 and pipe lines 42 and 43 to a
negative pressure outlet 15 provided in pipe 2. A switching valve 44, such
as a solenoid valve, is provided on line 42 and makes passages a and b
connecting lines 43 and 42 communicate with each other only when an
ignition switch 45 is switched on. When switch 45 is switched off, valve
44 interrupts passages a and b from each other, and instead makes passages
c and b communicate with each other.
Passage c is connected through a branch pipe line 51 to the negative
pressure outlet 15 through a negative pressure reservoir 46 and a delay
valve 47 opened by the negative suction pressure. Valve 47 is provided
with a sintered metal orifice 49 and an air filter 50, together with an
umbrella valve type check valve 48 opening to accumulate the negative
pressure in reservoir 46 in case the negative suction pressure is higher
than the negative pressure in reservoir 46.
Chamber E is connected through an opening 53 to the downstream side of
valve 44 through a branch pipe line 52 in which are provided a switching
valve 54, such as a solenoid valve or the like, and a delay valve 56.
Valve 54 is provided with passages d, e and f. Passage f communicates with
the atmosphere through an air filter 55. When switch 45 is switched on,
passages d and e only communicate with each other to make chamber E
communicate with line 42. When switch 45 is switched off, the passages d
and e are interrupted from each other, and passages e and f only
communicate with each other to make chamber E communicate with the
atmosphere. Valve 56 is provided with a sintered metal orifice 58 and an
air filter 59 together with an umbrella valve type check valve 57 opened
by the negative pressure in chamber E.
Valve 20 is provided with a valve mechanism for feeding secondary air into
pipe 8.
A case 61 is provided to form a chamber 62 below a partition wall 60
forming the bottom of chamber C. Chamber 62 is sectioned with a diaphragm
63 to provide a negative pressure chamber F and a chamber G communicating
with the atmosphere through an orifice 64. Chamber F is connected through
an opening 65 and pipe line 66 to communicate with line 43. A delay valve
67 is disposed in line 66, and provided with a sintered metal orifice 69
and air filter 70 together with an umbrella type check valve 68 opened by
the negative suction pressure in pipe 2. Diaphragm 63 is secured to the
lower end of a valve stem 71 which vertically passes through a stem guide
73 in a hole 72 of partition wall 60 and through chamber C. Stem 71 is
provided at its upper end with a valve body 74 opening and closing passage
25 between chambers B and C. Body 74 is resiliently pressed toward passage
25 through stem 71 by a spring 75 compressed and disposed within chamber
F.
The operation is described below. During general running, i.e., the
partially loaded running of the vehicle, throttle valve 6 is kept
partially open. As a result, high negative pressure to some extent is
generated downstream of valve 6, and the negative suction pressure acts on
chamber F through outlet 15, and lines 43 and 66. With this negative
pressure, diaphragm 63 is lowered against spring 75. Thereby, body 74 is
lowered through stem 71 to open passage 25, and chambers B and C
communicate with each other. Therefore, inlet 11 communicates with the
atmosphere through passage 25 and chamber B. Valve 13 is intermittently
opened by the pulsating pressure within pipe 8, and secondary air is led
into the exhaust gases from the atmosphere via chamber B, passage 25,
chamber C and line 31.
During general running of the vehicle, the negative suction pressure acts
also on chambers D and E through outlet 15, line 43, valve 44 and line 42.
However, the pressure difference to urge diaphragm 35 against the spring
load of spring 40 is not produced between both chambers D and E.
Therefore, due to spring 40, body 39 is moved up through stem 36 and
closes passage 23 to seal chambers B and A from each other.
When the vehicle decelerates, the opening angle of valve 6 becomes
considerably small as shown, and the negative pressure in outlet 15
increases. This negative pressure is transmitted to chamber D via lines 43
and 42. On the other hand, as chamber E is provided with valves 54 and 56
within branch line 52 connecting with line 42, the umbrella valve 57
closes by the negative suction pressure. The negative pressure therefore
acts gradually on chamber E through orifice 58 to produce a time lag
between the introduction of the negative pressure into chambers D and
chamber E. Therefore, chamber D first increases in negative pressure,
diaphragm 35 is flexed and lowered against spring 40 so that stem 36 will
also be lowered, and body 39 moves apart from the valve seat on the lower
surface of passage 23 and is pushed down to make chambers A and B
communicate with each other.
By the negative suction pressure during the normal cruising, body 74 is
kept lowered to open passage 25 and make chambers B and C communicate with
each other. But since body 39 is lowered, as described above, to open
passage 23 and make chambers A and B communicate with each other and is
further lowered to seat on the upper surface of passage 25 to close it,
the communication between chambers B and C is interrupted.
Thus, with the detection of the negative suction pressure at deceleration,
the relations of chambers A, B and C at the time of normal cruising is
switched over, and chambers B and C are interrupted. With this
interruption of chambers B and C, the feeding of air into the secondary
air feeding system is also interrupted. At the same time, with
communication between chambers B and A, secondary air is fed into pipe 2
through line 27 and inlet 14, and is mixed with the rich mixture produced
by the evaporated fuel on the suction pipe wall to dilute the mixture
before coming into the combustion chamber at the time of the deceleration,
i.e., when valve 6 is closed immediately from the normal running state.
Thus, at deceleration, secondary air is interrupted from being fed into
pipe 8 and is fed to the downstream side of the valve 6 to prevent
after-burning and to attain optimum combustion in the combustion chamber.
Secondary air is supplied to pipe 2 only in the initial period of
deceleration. With the action of valve 56, the negative pressure in
chamber E increases gradually. After the lapse of a certain period, the
negative pressures in chambers E and D equalizes. With the action of the
spring, diaphragm 35 moves up and body 39 closes passage 23 to interrupt
again communication between chambers A and B, to interrupt the feeding of
secondary air into the suction passage, and to prevent the dilution of the
mixture over a long period during deceleration.
The operation at the time of stopping the engine is described below.
When switch 45 is switched off to stop the engine, valve 44 is switched
over to make passages c and b communicate with each other. The negative
pressure accumulated within negative pressure reservoir 46 is led into
chamber D through passages c and b and the downstream side of line 42, and
immediately moves diaphragm 35 down to depress body 39 and open passage
23. Chambers A and B communicate with each other to allow secondary air
flow into pipe 2 through line 27 and inlet 14 so that this part reaches
atmospheric pressure. The fuel sucked into the combustion chamber is thus
diluted by the momentum of the engine. The mixture discharged into the
exhaust passages becomes lean. After-burning is thus prevented.
When body 39 moves down, passage 25 is closed, and chambers B and C are
interrupted from each other to stop the feeding of secondary air into the
exhaust passage. Therefore, the after-burning prevention is further
improved.
If this condition is continued, the evaporated fuel on the suction passage
wall leaks out into the atmosphere. However, the invention operates as
follows to prevent this.
As valve 47 is provided with orifice 48 in parallel with valve 48, the
atmospheric pressure led into outlet 15 is in turn introduced into chamber
46 through orifice 49. The negative pressure in chamber D is thus
gradually reduced. Diaphragm 35 moves up due to the action of the spring.
Body 39 moves up to close passage 23 and chambers A and B are interrupted
from each other. In other words, when the ignition key is switched off,
valve 20 is switched by the accumulated negative pressure to feed
secondary air into the intake passage, but this secondary air feeding
system operates only for a certain period and the suction passage is
interrupted from the atmosphere after the lapse of a certain period. Even
if the intake passage communicates with the atmosphere when the ignition
key is switched off, this sytem is closed so that the evaporated fuel
cannot leak out into the atmosphere.
When switch 45 is switched off, valve 54 makes a switching operation to
make passages f and e communicate with each other. Atmospheric pressure is
then introduced into chamber E so that diaphragm 35 will be quickly moved
down by the introduction of negative pressure into chamber D, and
secondary air will be quickly introduced into the intake passage. Thus,
when the engine stops, the above described effect can be attained
reliably.
If desired, an air pump can be used to feed secondary air into the exhaust
pipe.
Also, the negative pressure operation is made with the diaphragm in the
illustrated embodiment, but a piston may alternatively be used.
In the illustrated embodiment, the negative valve 20 is used also to
interrupt secondary air from the exhaust passage and to put secondary air
into the intake passage when the engine stops. However, such structure is
not necessarily required. Alternatively, the valve may be driven by the
negative pressure in the negative pressure reservoir, as operatively
connected with the switching off of the ignition switch, to establish a
feeding system of secondary air into the suction passage and, after the
lapse of a certain period, the system may be interrupted.
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