U.S. patent number 3,556,064 [Application Number 04/811,749] was granted by the patent office on 1971-01-19 for air pollution preventive device for spark-ignition-type internal combustion engines.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Tasuku Date, Akira Ishizuya, Tomoko Kikuraku, Norimitsu Kurihara, Toshio Shioya, Nobuyuki Togashi, Shuichi Yamazaki.
United States Patent |
3,556,064 |
Date , et al. |
January 19, 1971 |
AIR POLLUTION PREVENTIVE DEVICE FOR SPARK-IGNITION-TYPE INTERNAL
COMBUSTION ENGINES
Abstract
A device is provided for an internal combustion engine to
prevent air pollution thereby and the device comprises a
throttle-valve-actuating member connected to a throttle valve
vacuum actuator operable by increase in intake vacuum on the
downstream side of a throttle valve. The vacuum actuator is
releasably connected to the valve-actuating member so as to
maintain driving engagement with the actuating member only when the
throttle valve is nearly closed. An operating member of the
throttle valve, controlled by an accelerator pedal, is pivotably
interconnected with the throttle-valve-actuating member via a lost
motion connection of limited clearance so that when the throttle
valve is in nearly closed condition, the actuating member is
operable by the vacuum actuator upon increase in intake vacuum to
open the throttle valve while allowing the operating member of the
throttle valve to remain in inoperative position. With the
operating member remaining in its inoperative position; a further
device acts to retard the ignition timing of the engine.
Inventors: |
Date; Tasuku (Tokyo,
JA), Yamazaki; Shuichi (Iruma-gun, Saitama-ken,
JA), Togashi; Nobuyuki (Tokyo, JA), Shioya;
Toshio (Ohmiya-shi, JA), Kikuraku; Tomoko
(Iruma-gun, Saitama-ken, JA), Kurihara; Norimitsu
(Kitaadachi-gun, Saitama-ken, JA), Ishizuya; Akira
(Kitaadachi-gun, Saitama-ken, JA) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JA)
|
Family
ID: |
27520375 |
Appl.
No.: |
04/811,749 |
Filed: |
April 1, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Apr 4, 1968 [JA] |
|
|
43/21813 |
|
Current U.S.
Class: |
123/329;
261/DIG.19; 477/100; 477/102; 477/111 |
Current CPC
Class: |
F02P
5/06 (20130101); F02P 5/155 (20130101); F02M
19/122 (20130101); F02M 3/07 (20130101); F02D
37/02 (20130101); F02P 7/0637 (20130101); Y10T
477/663 (20150115); Y10S 261/19 (20130101); Y02T
10/46 (20130101); Y10T 477/68 (20150115); Y02T
10/40 (20130101); Y10T 477/67 (20150115) |
Current International
Class: |
F02D
37/00 (20060101); F02P 7/00 (20060101); F02M
19/00 (20060101); F02M 3/07 (20060101); F02M
19/12 (20060101); F02D 37/02 (20060101); F02P
5/04 (20060101); F02P 5/145 (20060101); F02P
7/063 (20060101); F02P 5/155 (20060101); F02P
5/06 (20060101); F02M 3/00 (20060101); F02p
005/04 (); F02d 031/00 () |
Field of
Search: |
;123/97B,97,117.1,117,102,148AC,148DS,146.5A,119 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Burns; Wendell E.
Claims
We claim:
1. An air pollution preventive device for a spark-ignition-type
internal combustion engine, comprising a throttle-valve-actuating
member connected to a throttle valve vacuum actuator means operable
by increase in intake vacuum on the downstream side of a throttle
valve and releasably connected with said throttle-valve-actuating
member so as to maintain driving engagement therewith only when the
throttle valve is nearly closed, a throttle-valve-operating member
operable by an accelerator pedal control and pivotally
interconnected with said throttle-valve-actuating member by lost
motion means of limited clearance, when the throttle valve is in
nearly closed position, said throttle-valve-actuating member being
operable by said vacuum actuator means with increase in intake
vacuum to open the throttle valve while allowing said
throttle-valve-operating member to remain in inoperative position
when the throttle valve is in nearly closed position, and means for
retarding the ignition timing of the engine relative to the normal
ignition timing thereof when said throttle-valve-operating member
is in inoperative position.
2. A device as claimed in claim 1, comprising first contact breaker
means adapted to advance the ignition timing with increase in
engine speed when the engine is in the state of normal drive,
second contact breaker means arranged for ignition timing retarded
relative to that of said first contact breaker means, and electric
switch means arranged between said first and second contact breaker
means and operable in association with the accelerator pedal
control to render said first and second contact breaker means
alternately effective.
3. A device as claimed in claim 1, in which said
throttle-valve-actuating and operating members are not only
operably interconnected by lost motion means of limited clearance
but are also interconnected by a tension spring that is weaker than
a return spring provided for said throttle-valve-operating
member.
4. A device as claimed in claim 1, further comprising a means to
resist initial returning movement of said throttle-valve-actuating
member when the throttle valve is allowed to return quickly to the
vicinity of its fully closed position.
5. A device as claimed in claim 1, comprising a combined vacuum
actuator and dashpot assembly including: a vacuum actuator section
including a spring-loaded diaphragm formed with a stop surface and
a vacuum inlet formed on one side thereof to receive intake vacuum
of the engine; a dashpot section arranged in axially adjacent
relation to said vacuum actuator section and including a
spring-loaded diaphragm; and a plunger rod slidably arranged on a
common axis of said sections and secured to the dashpot diaphragm,
said plunger rod being adapted to advance with closing movement of
the throttle valve and carrying a stop member for abutting
engagement with said stop surface on said actuator diaphragm.
6. A device for automotive use as claimed in claim 1, further
comprising vacuum switching means inserted in the line of intake
vacuum leading to said vacuum actuator means and operable at
appropriate times to render said vacuum actuator means
ineffective.
7. A device as claimed in claim 6, further comprising means for
detecting load on the engine, said detecting means being operably
connected with said vacuum switching means in a manner such that
said vacuum actuator means remains inoperative as long as the
engine is not loaded.
8. A device as claimed in claim 2 further comprising: means for
maintaining the operation of said second contact breaker means for
an initial period of movement of the throttle valve from small to
wide opening and then rendering said first contact breaker means
effective in the place of said second contact breaker means; and
means for advancing the ignition timing of said second contact
breaker means as the opening of the throttle valve increases in
said initial period.
9. A device as claimed in claim 2, comprising a parallel
arrangement of said first and second contact breaker means in the
primary side of the ignition coil, said second contact breaker
means being adapted to break later than said first contact breaker
means while the latter is open, said electric switch means being
inserted in the circuit of said second contact breaker means so as
to connect only said first contact breaker means to the ignition
coil when thrown open and to connect both said first and second
contact breaker means to the ignition coil when closed.
Description
As known, during the idling of internal combustion engines such as
for automotive vehicles, the throttle valve is fully closed and the
amount of air intake is reduced so as to cause incomplete fuel
combustion with the result that the engine exhaust tends to pollute
the atmosphere. Also, when the throttle is rapidly closed during
high-speed travel for quick retardation, the air intake is reduced
to a greater extent resulting in severe pollution of the
atmosphere.
The present invention has for its object to provide a simple and
effective device which is designed to prevent excessive reduction
in the amount of air intake with the engine idling and upon quick
retardation thereby to prevent air pollution attributable to the
engine exhaust and is operable on those occasions to retard the
ignition timing thereby to reduce the engine power output for
smooth idling and effective rapid retardation of the engine.
Another object of the present invention is to provide an air
pollution preventive system of the character described which is
designed particularly to prevent the throttle valve from being
closed completely even for a short period of time and thus is
effective to prevent air pollution otherwise resulting from such
complete throttle closing.
These and other objects, features, and advantages of the present
invention will become apparent from the following description when
taken in conjunction with the accompanying drawings, which
illustrate a few preferred embodiments of the invention and in
which:
FIG. 1 is a partly schematic illustration of one embodiment of the
invention;
FIG. 2 illustrates another embodiment in which the throttle valve
is prevented from being closed completely when released to rapidly
close;
FIG. 3 is a fragmentary illustration looking in the direction of
the arrow III in FIG. 2;
FIG. 4 illustrates a modification of the device shown in FIG.
2;
FIG. 5 is an axial cross-sectional view showing a simplification of
the device shown in FIG. 4.
FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG.
5;
FIG. 7 is a partly, schematic illustration of a modification of the
device shown in FIG. 1, in which the vacuum actuator is rendered
ineffective at appropriate times;
FIG. 8 is an axial cross-sectional view of a form of switching
means operable in association with the clutch in the engine
transmission;
FIG. 9 is a view similar to FIG. 9, showing a form of switching
means operable in association with the speed change gear;
FIG. 10 is a partly cutaway view showing a contact breaker unit
improved over the one shown in FIG. 1;
FIG. 11 is an axial cross-sectional view of the unit;
FIG. 12 is an illustration of a further embodiment of the
invention, which includes, among others, switching means operably
connectable with the contact breaker unit shown in FIGS. 10 and
11;
FIG. 13 is a diagrammatic chart showing the mode of operation of
the device shown in FIG. 12;
FIG. 14 is an ignition circuit diagram of the device of the
invention;
FIG. 15 is a diagram illustrating the operation of the ignition
circuit;
FIG. 16 illustrates a modification of the circuit shown in FIG.
14;
FIG. 17 illustrates a conventional circuit formation; and
FIG. 18 is a cross-sectional view taken along line XVIII-XVIII in
FIG. 11.
Referring to the drawings and first to FIG. 1, reference numeral 1
designates an intake duct; and 2 a throttle valve with its shaft 3
pivotally supported in the intake duct 1. Numeral 4 indicates a
throttle-valve-actuating member fixed to the throttle shaft 3
outside of the intake duct, with a projecting stud pin 5 and a
slotted piece 6 firmly secured to the actuating member 4 at its
opposite ends. An elongated slot 7 is formed in the piece 6.
Pivotally mounted on the throttle shaft 3 is a
throttle-valve-operating member 8, to which is connected a throttle
wire 9, which is connected to accelerator pedal means (not shown).
A relatively strong return spring 11 is arranged between the
throttle-valve-operating member 8 and a fixed support or bracket 10
with a stop 12 adjustably threaded in and extending through the
bracket 10 for abutting engagement with an abutment 8A formed on
the adjacent portion of the member 8. The throttle-valve-operating
member 8 is also formed with an aperture 13 to loosely receive the
stud pin 5 and a relatively weak tension spring 14 is arranged
between the members 4 and 8 so that, when the vacuum actuator 16 is
in inoperative position, the pin 5 is held in contacting engagement
with the wall of the aperture 13 at point 15 under the tension of
spring 14, connecting the throttle-valve-operating member 8
integrally with the throttle-valve-actuating member 4 and throttle
valve 2. In this state, it will be apparent that, when throttle
wire 9 is drawn to rotate the throttle-valve-operating member 8,
the throttle valve 2 is opened correspondingly and, when the wire 9
is released, the member 8 is restored under the tension of the
return spring 11 into engagement with the stop 12 and the throttle
valve 2 is restored to its minimum opening. It is to be understood
that the stop 12 is set in advance so that even during engine
idling with such minimum throttle opening, the amount of air intake
is not reduced to any excessive extent.
Reference numeral 16 indicates a vacuum actuator formed with a
vacuum inlet 17, which is connected with the intake duct through a
vacuum takeout port 18 formed therein on the downstream side, i.e.,
the engine side of the throttle valve 2. Provided in the vacuum
actuator 16 is a diaphragm 20 loaded with a compression spring 19
and secured to an actuator rod 21, which is loosely fitted close to
its extreme end through the slot 7 in the piece 6 and carries at
its extremity an enlarged engaging head 22 for releasable
engagement with the throttle-valve-actuating member 4. As shown, an
adjustable stop 23 is provided on the vacuum actuator 16 for
limiting the movement of the actuator rod 21. With this
arrangement, it will be noted that, during high-speed engine
operation, when throttle wire 9 is released to allow the
throttle-valve-operating member 8 to rapidly restore its
inoperative position engaging stop 12, the vacuum in the intake
duct is increased and, overcoming the bias of compression spring
19, causes the actuator rod 21 and hence its engaging head 22 to
move upwardly, as viewed in FIG. 1. Consequently, the engaging head
22, being placed in engagement with the slotted piece 6, turns the
throttle-valve-actuating member 4 counterclockwise relative to the
throttle-valve-operating member 8 against the bias of tension
spring 14 with the result that the opening of the throttle valve 2
is maintained above its minimum to prevent any excessive reduction
in amount of air intake. On this occasion, pin 5 is moved away from
the point of contacting engagement 15 against the relatively weak
tension spring 14, as indicated by the chain line 5A by of the
space C provided in aperture 13 for such lost motion of pin 5. On
the other hand, the throttle-valve-operating member 8 remains in
its released or inoperative position under the bias of return
spring 11, which is stronger than tension spring 14.
It will be noted that, in this situation, when the throttle wire 9
is subsequently drawn to turn the throttle-valve-operating member 8
to a substantial extent, pin 5 is placed again in contacting
engagement with the aperture 13 and the slotted piece 6 is released
from the engaging head 22 of the actuator rod 21 so that the
throttle valve 2 can be operated under the control of the
accelerator pedal means.
Referring again to FIG. 1, reference numeral 24 indicates the
casing of a contact breaker unit which includes a cam shaft 25
rotatable at a speed proportional to the engine speed with a
breaker cam member 26 mounted on the cam shaft 25 for rotation
therewith. The cam member 26 is also arranged in the conventional
manner to rotate relative to the cam shaft 25 with variation of the
engine speed, thus varying the relative angular phase between the
two members 26 and 25.
Reference numeral 27 indicates a rotative disc provided in casing
24 and rotatable about the axis of cam shaft 25. Pivotally mounted
on the rotative disc 27 at 29 is a first contact breaker arm or
element 28 which is formed at one end with a slide finger 28A for
sliding engagement with the camming surface of cam 26 and carries
at the other end a movable contact 28B, which is cooperable with a
fixed contact 30. Numeral 31 indicates a leaf spring provided to
normally hold the movable contact 28B in pressure engagement with
the fixed contact 30. The movable contact 30 and leaf spring 31 are
mounted on rotatable disc 27.
Pivotally mounted in the casing 24 at 33 is a second contact
breaker arm or element 32 in an angular position retarded relative
to that of first contact breaker arm 28. The second breaker element
32 is formed at one end with a slide finger 32A for sliding contact
with the camming surface of cam 26 and carries at the other end a
movable contact 32B, which cooperates with a fixed contact 34. A
leaf spring 35 is provided to normally hold the movable contact 32B
in pressure contact with the fixed contact 34. A plunger or push
rod 36, forming part of an appropriate vacuum actuator (not shown),
is pivotally connected with the rotative disc 27 so as to rotate
the rotative disc 27 under the control of vacuum led from the
vicinity of throttle valve 2 in the intake duct. Thus, when the
first breaker element 28 is connected in the ignition circuit, as
will be described hereinafter, the ignition timing of the engine as
obtained with the breaker element 28 is advanced or retarded in the
conventional manner in accordance with the engine speed and also
with the intake vacuum from the vicinity of throttle valve.
Incidentally, the rotative disc 27 may be omitted, if desired, with
the first breaker element 28 directly pivoted to the breaker
casing. Also, with the provision of rotative disc 27, the second
breaker element 32 can be pivotally mounted on the disc 27 together
with the first breaker element 28.
Reference numeral 37 generally indicates a switching device fixed
relative to the intake duct 1 and including an insulating slide pin
38 which carries a headpiece 39 and a short-circuiting ring 42. The
slide pin 38 is provided with a spring 40 which acts to bias the
slide pin 38 normally to hold its headpiece 39 in its outwardly
extended position. Carried on the slide pin 38 is an adjustable
stop 41 which serves to limit the extent of projection of the
headpiece 39. The switching device 37 also includes an electrode
strip 43 which is continuously in connection with short-circuiting
ring 42 and further electrode strips 44 and 45 which are placed
alternately in connection with short-circuiting ring 42, with
conducting wires 46, 47 and 48 connected to the electrode strip 43,
45 and 44, respectively. As shown, the slide pin headpiece 39 is
located opposite the abutment 8A of the throttle-valve-operating
member 8 and, when the latter 8A is in abutting engagement with
stop 12, the slide pin 38 is held in the shown position with the
short-circuiting ring 42 placed in contact with the electrode strip
44 as well as with electrode strip 43. It will be understood that
the short-circuiting ring 42 is brought into connection with the
electrode strip 45 in place of the strip 44 when the abutment 8A is
moved apart from stop 12 to release the slide pin 38.
Reference numeral 49 indicates the ignition circuit of the
internal-combustion engine; 50 an ignition coil in the circuit; 51
a distributor; and 52 represent spark plugs of the engine. The
aforesaid conducting wire 46 is connected to the ignition coil 50
and conducting wire 47 is connected to movable contact 28B of the
first breaker 28 through leaf spring 31 while the remaining
conducting wire 48 is connected to the movable contact 32B of the
second breaker 32 through leaf spring 35. With this arrangement it
will be noted that the ignition timing is retarded when the
abutment 8A is in abutting engagement with stop 12, that is, when
the throttle-valve-operating member 8 is in its inoperative
advanced position but, when the member 8 is in operation, the
ignition timing is advanced conventionally according to the engine
speed.
With the inventive device constructed and arranged in the manner
described, it will be appreciated that even when the internal
combustion engine is idling the amount of air intake is kept
relatively large, enabling relatively efficient fuel combustion and
substantially eliminating rod to turn the throttle-valve-actuating
danger of the engine exhaust polluting the atmosphere and that on
this occasion the engine idling can be kept smooth with or abnormal
rise in the engine speed since the throttle-valve-operating member
8 is in its inoperative position with the ignition timing retarded
to reduce the engine power output. Also, when the
throttle-valve-operating member 8 is released during high-speed
engine operation to its inoperative position to rapidly close the
throttle valve 2 for quick deceleration of the engine operation,
the vacuum actuator 16 is immediately operated causing the engaging
head 22 of the actuator rod to turn the throttle-valve-actuating
member 4 to a position to hold the opening of the throttle valve 2
at a value larger than that during the engine idling. In this
manner, the amount of air intake is kept from being reduced
excessively and efficient fuel combustion is obtained eliminating
the danger of the engine exhaust polluting the atmospheric air.
Moreover, on this occasion, the lost motion provided between the
throttle-valve-actuating member 4 and throttle-valve-operating
member 8 allows the latter to remain in its inoperative position
and maintain the retarded ignition timing and correspondingly
reduced engine output, enabling rapid and smooth deceleration of
the engine. Also, the arrangement of first and second contact
breakers operable in association with accelerator pedal means
enables rapid and accurate reduction in engine output. Further, the
provision of two weak and strong springs 14 and 11 associated with
the throttle-valve-actuating and operating members enables the
vacuum actuator 16 to open the throttle valve 2 by tensioning only
the weak tension spring 14 without tensioning the strong return
spring 11 for the throttle-valve-operating member 8 thus making the
action of the vacuum actuator and smooth thereof. In addition,
since the tension spring 14 remains unchanged in length and hence
in tension even when the throttle-valve-operating member 8 is
varied in position, the vacuum actuator 16 can operate the
throttle-valve-actuating member 4 at all times with a definite
force and with accuracy.
With the device described above, however, when the
throttle-valve-operating member 8 is rapidly operated, the throttle
valve 2 may initially be fully closed, though only for a short
period of time, with the result that the amount of air intake per
engine cycle is reduced to such an extent as to cause incomplete
fuel combustion, allowing the engine exhaust to severely pollute
the atmosphere. This difficulty can be overcome by the device shown
in FIGS. 2 and 4.
Referring to FIGS. 2 and 4, the shaft 3 of throttle valve 2 is
formed at one end with a short arm 63 which carries a pin 5. This
pin 5 is loosely fitted in an aperture 13 formed in the
throttle-valve-operating member 8 as in the previously described
embodiment. Throttle-valve-actuating member 64 is firmly secured to
the other end of the throttle valve shaft 3. Reference numeral 62
indicates a carburetor; and 65 a first vacuum actuator with its
vacuum inlet port 66 connected to the intake duct 1 at the vacuum
takeout port 18. Provided in the vacuum actuator 65 is a diaphragm
68 to which an actuator rod 69 is secured. Numeral 70 indicates a
biasing spring provided on the actuator to urge the actuator rod 69
outwardly thereof; and 67 indicates a vent hole. As shown in FIG.
3, an engaging piece 71 is fixed to the actuator rod 69 at its
extreme end for engagement with an abutting bolt 73 threadably
fitted on a support plate 72, which is fixed to the
throttle-valve-operating member 64.
Reference numeral 74 generally indicates a second vacuum actuator
having a vacuum inlet port 75 connected to the intake duct 1 at
vacuum takeout 18. Provided in the vacuum actuator 74 is a
diaphragm 78 urged in a one direction by a weak spring 76 and
formed with a small aperture 77. An actuator rod 79, secured to the
diaphragm, carries an adjustable engaging rod 80 threadably fitted
in the actuator rod 79 for abutting engagement with support plate
72. Numerals 74A and 74B indicate air chambers formed on the
opposite sides of diaphragm 78 and communicating with each other
through aperture 77 formed therein; and numeral 81 indicates an
adjustable stop provided to limit the extent of movement of the
diaphragm 78 under vacuum.
The device described above operates as follows:
When at high engine speeds the throttle wire is released for rapid
deceleration of the engine, the throttle-valve-actuating member 64
is restored under the bias of return spring 11 to rapidly close the
throttle valve 2 and thus the intake vacuum in the vicinity of
vacuum takeout 18 increases so that the actuator rod 69 is moved
upward, as viewed in FIG. 2, through the intermediary of diaphragm
68, and thus restricts the downward pivotal movement of the
throttle-valve-actuating member 64, precluding the total closure or
throttle valve 2 and hence excessive reduction in the amount of air
intake. In this connection, the biasing spring 70 in first vacuum
actuator 65 is set to exhibit a relatively large bias so as not to
be susceptible to the intake vacuum occurring during the engine
idling or ordinary cruising operation. It will be noted, therefore,
that, even when the throttle valve 2 is rapidly closed for rapid
deceleration of the engine and the intake vacuum is increased to
some extent, the first vacuum actuator 65 will not operate
immediately following the throttle closing, allowing the throttle
valve 2 to close completely for a brief period of time, and this
might result in excessive reduction in the amount of air intake,
necessarily allowing the engine exhaust to pollute the atmosphere,
a difficulty which is found with the device shown in FIG. 1.
In the device shown in FIGS. 2 to 4, however, the above difficulty
is effectively overcome by the provision of second vacuum actuator
74 provided with relatively weak spring 76, which is lightly
deformable under intake vacuum. Thus, when the intake vacuum in the
vicinity of vacuum takeout 18 is increased, the diaphragm 78 of the
actuator will immediately be operated causing the actuator rod 80
to rise before the actuator rod 69 and hence engaging piece 71 of
the first vacuum actuator will start to rise. In this manner, when
the throttle-valve-actuating member 64 is rapidly turned
downwardly, the support plate 72 is brought into collision contact
with the actuator rod 80 to vigorously depress the associated
diaphragm 78, and the air in chamber 74B, increasing in pressure
relative to that in chamber 74A, is urged to flow into the latter
through small aperture 77 formed in the diaphragm 78. It is to be
recognized, however, that the airflow is restricted by the limited
size of aperture 77 and this together with the increase in pressure
in chamber 74B precludes any substantial descent of the
throttle-valve-actuating member 64 and hence the total closing of
the throttle valve 2 for a while. In the meantime, the intake
vacuum increases to start operation of the first vacuum actuator 65
to raise the engaging piece 71 into abutting engagement with
support plate 73 and thus preclude any further descent of
throttle-valve-actuating member 64, thus preventing the throttle
valve from being closed completely. After the rapid downward
pivotal movement of throttle-valve-actuating member 64, the vacuum
pressure is substantially balanced between the air chambers 74A and
74B and, with the limited spring rate of actuator spring 76, the
second vacuum actuator 74 is rendered substantially inoperative,
placing the throttle valve 2 under the control of the first vacuum
actuator 65 only.
As apparent from the foregoing, this embodiment of the present
invention is advantageous in that it is designed to prevent the
intake throttle valve from being completely closed even in the
initial period of rapid deceleration of the internal combustion
engine and thus effectively prevents air pollution as caused by the
engine exhaust.
Incidentally, the second vacuum actuator 74 may also be operated,
for example, when the throttle valve is rapidly closed for the
shifting of the speed change gear but this will cause no trouble to
the engine operation as the system is restored immediately.
FIG. 4 illustrates a modification of the device shown in FIG. 2,
employing instead of second vacuum actuator 74 a flow resistor 82
operable independently from the intake vacuum. The resistor 82
includes a diaphragm 84 biased by a relatively weak spring 83 and
secured to an abutment rod or plunger 85. The air chamber 82B,
defined on the underside of diaphragm 84, is vented by a small
aperture 86 while the air chamber 82A overlying the diaphragm is
vented by a large-diameter aperture 87. With this arrangement, when
the throttle-valve-actuating member 64 is rapidly moved downward
bringing the support plate 72 thereon into contact with the plunger
85, the diaphragm 84 is vigorously lowered and the pressure in the
air chamber 82B is increased by virtue of the resistance of the
small vent aperture 86 to the airflow and thus precludes any
further downward movement of the throttle-valve-actuating member
64. Subsequently the air pressure is balanced between the two air
chambers 82A and 82B and, with the limited spring rate of
associated spring 83, the throttle-valve-actuating member 64 can be
operated substantially freely despite the provision of the flow
resistor 82. In this manner, it will appreciated that the device of
FIG. 4 functions with the same advantageous effect as the device of
FIG. 2.
A further modification of the device shown in FIG. 4 is shown in
FIGS. 5 and 6, which is compact and simple in structure compared
with the FIG. 4 device, including a single plunger or actuator rod
corresponding in effect to a combination of the actuator rod 69 of
the first vacuum actuator 65 and the plunger 85 of resistor 85 in
FIG. 4.
Referring to FIGS. 5 and 6, the combined actuator-resistor unit
shown therein includes a vacuum actuator section A and a
dashpot-type resistor section B, and the former includes a casing
101 and a diaphragm 104, which is provided with a stop surface 102
and a return spring 103 and defines two chambers 105 and 106 on the
opposite sides of the diaphragm. One of the chambers 105 is
provided with a vacuum inlet port 107 to receive the intake vacuum.
The dashpot section B includes a casing 108 and a diaphragm 110
arranged therein to define two chambers 111 and 112 on the opposite
sides thereof and provided with a return spring 109. A vent hole
113 is formed in the dashpot B to communicate one of the chambers
111 with the atmosphere. As shown, the actuator and resistor
sections A and B of the unit are arranged axially adjacent to each
other and a common plunger rod 116 is slidably fitted through axial
holes 117 and 118 formed in the respecting casings 101 and 108. The
plunger rod 116 is arranged so as to be advanced upon closing of
the throttle valve 144 under the bias of return spring 115 provided
therefor. The plunger rod 116 carries a stop ring 109 for
cooperation with the stop surface 102 on the actuator diaphragm 104
and, extending loosely through the latter, is secured to the
resistor diaphragm 110. The shaft 120 of the throttle valve 114
carries at its extended end a lateral arm 121 fixed thereto with
the outer end of the arm 121 lying opposite the adjacent extreme
end of plunger rod 116 for pressure engagement therewith. Numeral
122 indicates a throttle-valve-actuating member secured to the
throttle valve shaft 120 at its opposite end; 123 is a return
spring provided for the member 122; 124, 125 are vent holes
respectively communicating the chambers 106 and 112 to the
atmosphere; and 126 is a valve provided to allow air exhaust only
from chamber 111. The axial arrangement on the plunger rod 116 can
be reversed, if desired.
In the operation of the device of FIGS. 5 and 6, when the throttle
valve 114 is allowed to close under the bias of return spring 115,
the plunger rod 116 is advanced to the right as viewed in FIG. 5
but slowly against the resistance of the dashpot B, taking more or
less time to make a predetermined length of travel. Accordingly,
the intake vacuum is allowed to increase with a more or less delay
and subsequently causes the vacuum actuator A to operate to
displace the stop surface 112 of the diaphragm therein to the left
as viewed in FIG. 5. The stop ring 119 on the plunger rod 116 being
advanced is thus engaged by the stop surface 112 of the diaphragm
now displaced to the left and the advancing movement of the plunger
rod 116 and hence the closing motion of the throttle valve 114 are
hampered. In other words, the throttle valve 114 cannot be closed
completely but is only brought to a slightly open position.
In use of the device shown in FIG. 1 another inconvenience is
encountered as described below. In the case of no-load engine
operation, as when the clutch means between the engine and its load
is disengaged or when the transmission is rendered neutral, and in
the case of low-output engine operation, employing lower speed
transmission gear trains, the vacuum actuator may possibly be
rendered operative to prevent the throttle valve from being closed
completely, causing undesired increase in engine speed and thus
inconvenience in the driving operation.
FIGS. 7 to 9 illustrate a device designed to overcome such
inconvenience by rendering the vacuum actuator inoperative in cases
such as mentioned above.
Reference will first be made to FIG. 7, in which reference numerals
1 to 36 indicate parts corresponding to the same reference numerals
in FIG. 1. In FIG. 7, the push rod 36 is pivotally connected at 137
to the rotative disc 27 and secured to the diaphragm 139 of a
vacuum actuator 138, which has a vacuum inlet port 140 formed
thereon to receive the intake vacuum from a vacuum takeout port
(not shown) provided in the vicinity of the throttle valve 2.
Numeral 141 indicates a pressure spring engaging the actuator
diaphragm 139. With this arrangement, the ignition timing, when the
first contact breaker 28 is in connection with the ignition
circuit, is advanced or retarded in accordance with the engine
speed as well as with the intake vacuum in the vicinity of the
throttle valve, in the same manner as described hereinbefore in
connection with the device of FIG. 1, but the timer construction is
different from that employed in the FIG. 1 device, as will be
described hereinafter.
Reference numeral 142 indicates a switching device secured to the
intake duct 1 and including two spring strips 143 and 144 with
their extreme ends joined to form a type of toggle joint. Also
included in the device 142 are a pin 145 provided to actuate the
spring strips, a contact 146 carried on one of the spring strips
143, an electrode or terminal plate 147 engageable with contact
146, and another electrode 148 connected with spring strip 143.
When the abutment 8A on the throttle-valve-operating member 8 is in
engagement with stop 12 or when the member 8 is in its inoperative
position, the contact 146 is closed in contact with the electrode
plate 147 and, when the member 8 is operated by means of throttle
wire 9, the contact 146 is opened away from the electrode 147. The
electrode plate 148 is connected through conducting wire 149 and
leaf spring 35 of the second breaker 32 to movable contact 32B
thereof while on the other hand the conducting wire 150 connected
to electrode plate 147 is also connected through wire 151 and leaf
spring 35 of first breaker 28 to movable contact 28B thereof.
Reference numeral 152 generally indicates the ignition circuit
including an ignition coil 153, a distributor 154 and spark plugs
155. The conducting wire 150 is connected also to the ignition coil
153, as shown.
Reference numeral 156 generally indicates a vacuum switching device
which includes a valve member having two valve heads 158 and 159
and biased downward as viewed in FIG. 7 by a spring 160 with an
electromagnet 157 serving, when energized, to lift the valve member
158-159. Connected to the device 156 are a conduit 161 leading from
the vacuum takeout port 18 of the intake duct, another conduit 162
leading to the vacuum inlet port 17 of vacuum actuator 16, and a
discharge pipe 163. As will be apparent, the electromagnet 157,
when energized, acts against the bias of spring 160 to lift the
valve member 185-159 and thus interconnects the conduits 161 and
162. When electromagnet 157 is deenergized, the valve member
158-159 is lowered under the bias of spring 160 and thus the vacuum
from conduit 161 is intercepted by the valve head 158, the vacuum
in conduit 162 being released to the atmosphere through the vent
hole 164 formed in the valve head 159 and through discharge pipe
163, rendering the vacuum actuator 16 inoperative. Conducting wires
165A and 165B are suitably arranged for energization of
electromagnet 157 with an electric switch 166 interposed between
the wires.
If the vacuum inlet port 17 of vacuum actuator 16 is continuously
connected to the vacuum, the throttle valve which is rapidly closed
for no-load engine operation with the clutch disengaged may at
times be increased and, thus energizing the vacuum actuator 16, the
opening of the throttle opening may be increased, unnecessarily
increasing the engine speed. Such undesired increase of engine
speed can be prevented with the provision of vacuum switching
device 156 and electric switch 166 therefor by arranging
appropriate means to detect the clutch state, and open the switch
166 when the clutch is in disengaged state.
FIG. 8 illustrates one example of such detecting means. In FIG. 8,
reference numeral 167 indicates the master cylinder of a
conventional clutching device with a piston 168 slidably arranged
in the cylinder. In the conventional manner, the clutch is
disengaged when the piston 168 is operated by means of a clutch
pedal (not shown) and the oil pressure in the cylinder 169 is
increased accordingly. In this instance, the increase in oil
pressure in the cylinder 169 also serves to move another piston 170
against the action of a biasing spring 171 provided therefor so
that a conducting ring 172 secured to the top of piston 170 is
raised to disconnect electrode strips 173 and 174, from each other
to which conducting wires 165A and 165B are connected. The
conducting ring 172 and electrode strips 173 and 174 together form
the above-mentioned switch 166.
Similarly, in no-load engine operation with the speed-change gear
in neutral position, the speed-change operation may at times be
made difficult by increase in engine speed if the vacuum inlet port
17 of vacuum actuator 16 is continually connected to the vacuum
takeout port 18 of the intake duct 1. This difficulty can be
overcome by employing appropriate detecting means operable upon
detection of the gear shifting to close the switch 166 for
energization of the vacuum switching device 156.
FIG. 9 illustrates one example of such detecting means and therein
reference numeral 175 indicates an oil passage so designed that the
oil pressure therein is increased upon completion of the gear
shifting. As will be readily observed, the pressure increase in the
oil passage 175 causes a piston 176 to move against the bias of a
return spring 177 and, as a result, a conducting ring 178 fixed to
the top end of the piston 176 is carried into a position to
interconnect electrode strips 179 and 180, to which conducting
wires 165A and 165B are connected, respectively. It will be
apparent that the conducting ring 178 and electrode strips 179, 180
together form the electric switch 166 mentioned hereinbefore.
Another difficulty which may possibly occur if the vacuum inlet
port 17 is continuously in connection with the vacuum takeout port
18 is that the vacuum actuator 16 may again inadvertently operate
during cruising to make the car speed control difficult. In
general, the cruising period of the car drive employing the
high-speed gear train is longer than that employing lower speed
gear trains and this fact makes it more important to prevent air
pollution during high-speed cruising than during low-speed drive.
Accordingly, the vacuum actuator 16 is usually set to operate
smoothly by the increase in intake vacuum occuring upon
deceleration during high-speed cruising.
Accordingly, during low-output low-speed cruising, which requires
only a limited throttle opening, the intake vacuum tends to acquire
a value higher than the value for the vacuum actuator setting
referred to above, causing the actuator 16 to operate to increase
the throttle opening. This results in the inconvenience that the
car speed can hardly be controlled in the manner desired by the
driver. Such inconvenience can be avoided by employing appropriate
means for detecting completion of the high-speed gear train thereby
to close the switch 166 and render the vacuum switching device 156
effective, thus precluding operation of the vacuum actuator 16
during the drive with any low-speed gear train completed.
It is to be noted that as such detecting means use can be made of
the device shown in FIG. 9 as long as it is adapted so that the oil
pressure in passage 175 is increased only with the high-speed gear
train completed.
Although the description has been made here assuming that the
electric switch 166 is operable by oil hydraulic means, it will be
apparent that the switch may be provided with any other type of
operating mechanism or be made manually operable, as desired.
Furthermore, with the device shown in FIG. 1 or FIG. 7, if the
throttle valve 2 is opened wide when the second contact breaker
element 32 is in operation with a small throttle opening, the
second breaker element 32 is quickly replaced by the first breaker
element 28 with the result that the ignition timing is
substantially instantaneously to rapidly increase the engine power
output exerting shock and other undesirable effects upon the engine
and the passengers in the vehicle.
FIGS. 10 to 13 illustrate a device modified to overcome the
deficiency described above and in which, when the throttle valve is
operated from small to large opening, the first breaker initially
remains ineffective, the second breaker continuing to operate but
with its ignition timing advanced at the instant of throttle
operation, and subsequently the first breaker is put into action
taking the place of the second breaker.
Referring to FIGS. 10, 11, and 18, which illustrate the breaker
unit of the device, reference numeral 201 indicates the casing of
the unit; 202 a breaker cam shaft rotatable at a speed proportional
to the engine speed; 203 a second breaker cam sleeve mounted on the
cam shaft; and 204 a first breaker cam sleeve mounted on the second
cam sleeve 203. As shown in FIGS. 11 and 18, cam plates 205 and 206
are secured to respective cam sleeves 203 and 204 and a support
plate 207 is fixed to cam shaft 202 with centrifugal advancing
weights 208 and 209 pivotally mounted on the support plate 207 and
carrying respective pins 208A and 209A for engagement with cam
plates 205 and 206, respectively. Fixed in the casing 201 are base
plates 210 and 211 on which respective annular rotative discs 212
and 213 are journaled. First and second breaker arms or elements
215 and 214 are pivotally mounted on the rotative discs 213 and 212
at 213A and 212A, respectively.
As shown in FIG. 10, the first breaker element 215 is formed at one
end with a slide finger 215A for sliding engagement with the
camming surface of the first cam sleeve 204 and carries at the
other end a movable contact 215B for cooperation with a fixed
contact 216. A leaf spring 217 is provided normally to hold the
movable contact 215B in pressure contact with the fixed contact
216. Similarly, the second breaker element 214 is formed at one end
with a slide finger 214A for sliding engagement with the camming
surface of second cam sleeve 203 and carries at the other end a
movable contact 214B for cooperation with a fixed contact 218. A
leaf spring 219 is provided normally to hold the movable contact
214B in pressure contact with the fixed contact 218. It is to be
understood that the second breaker 214 is retarded in ignition
timing relative to the first breaker 215.
Reference numeral 220 indicates an appropriate vacuum actuator
operable under the control of intake vacuum fed from the vicinity
18 of throttle valve 2 as shown in FIG. 12. The actuator 220 is
operably connected with the rotative disc 213 carrying first
breaker element 215 by way of an actuator rod 221 but this is not
always necessary.
Reference numeral 222 indicates a connecting rod pivotally secured
to the rotative disc 212, which carries the second breaker element
214. A tubular member 224 is provided to receive the extreme end
portion of the connecting rod 222 in sliding relation to the
enlarged head 223 thereof with a compression spring 225 arranged
between the head 223 and the bottom of the tubular member 224, as
shown. Connected to the tubular member 224 is a wire 226 which is
operable upon depression of the accelerator pedal (not shown).
Arranged between an abutment piece 227 extending laterally from the
connecting rod 222 and a fixed part 228 is a return tension spring
229 which is weaker than spring 225. The connecting rod 222 also
carries another abutment piece 230 which is normally held in
abutting engagement with said fixed part 228. Another fixed part
228A serves to limit the travel of the first-mentioned abutment
piece 227, as will be described below.
With this arrangement, it will be readily observed that when the
accelerator pedal is depressed, the connecting rod 222 is drawn
against the bias of spring 229 until the abutment piece 227 comes
into abutment against the fixed part 228A and with this motion of
the connecting rod 222, the annular rotative disc 212 is turned
carrying the second breaker 214 angularly relative to the
associated cam sleeve 203 to advance the ignition timing of the
breaker. Continued drawing of the wire 226 after the engagement of
abutment piece 227 with the fixed part 228A is only effective to
further compress the spring 225. In this situation, releasing the
accelerator pedal first allows the spring 225 to expand,
subsequently allowing the spring 229 to contract until the abutment
piece 230 is restored into engagement with fixed part 228 and in
this manner the second breaker 214 is restored to its initial
retarded position.
In FIG. 12, reference numerals 1 to 23 correspond to those in FIGS.
1 and 7. In the device of FIG. 12, however, the elongated aperture
13 is slightly enlarged in the direction of the point of contacting
engagement 15 as indicated by the chain line 243A, and an
adjustable stop 242A is provided for abutting engagement with the
throttle-valve-actuating member 4 against the bias of spring 14.
The adjustable stop 242A is set so as to provide a slight gap or
distance between the pin 5 and the wall 243A of the enlarged
aperture portion when the throttle-valve-actuating member 4 is in
engagement with the stop 242A. It will be apparent that this stop
device is effective to moderate the shock occurring when the
throttle-valve-operating member 8 is operated.
Referring again to FIG. 12, reference numeral 254 generally
indicates an electric switch fixed relative to the intake duct 1.
The switch 254 includes an insulating slide pin 255 having an
extended head 256 and biased by a spring 257 toward the abutment 8A
carried on throttle-valve-operating member 8 with the pin head 256
normally held in engagement with the abutment 8A under the spring
bias. As shown, the slide pin 255 carries a short-circuiting ring
259 and a stop 258. Reference numerals 260 and 261 indicate
respective electrode strips which are in contact with
short-circuiting ring 259 only when the throttle-valve-operating
member 8 is in abutting engagement with stop 12 or is spaced
therefrom by a small distance. This distance is determined by the
axial length Y of that portion of the short-circuiting ring 259
which extends from the point of contact 262 with the electrode
strips 260 and 261 toward the spring 257. Reference numeral 263
generally indicates the ignition circuit including an ignition coil
264, a distributor 265, spark plugs 266, and a voltage source 267.
As shown, one of the electrode strips 261 is connected through a
conducting wire 268 to the ignition coil 264. Another conducting
wire 269 connected at one end to the other electrode strip 260 is
connected at the other end to leaf spring 219, which is connected
to the movable contact 214B of second contact breaker 214. A
further conducting wire 270 connected at one end to the conducting
wire 268 is connected at the other end to the leaf spring 217
connected to the movable contact 215B of the first contact breaker
215. It will be obvious that short circuiting of electrode strips
260 and 261 made by the short circuit ring 259 renders the second
circuit breaker 214 effective to make spark ignition at plugs 266.
On this occasion, the first contact breaker 215 remains ineffective
even when its contacts 215B and 216 are opened since the primary
current of ignition coil 264 is not interrupted.
With the embodiment arranged as described above, it will be
observed that, when the accelerator pedal is released to place the
throttle-valve-operating member 8 in engagement with stop 12, the
electrode strips 260 and 261 are short circuited by the
short-circuiting ring 259 to render the second contact breaker 214
effective and thus the ignition timing is retarded. In addition on
this occasion the throttle opening is held at an appropriate level
by the provision of stop 242A and is properly increased with intake
vacuum. In this situation, it will be readily appreciated that
discharge of any engine exhaust tending to pollute the atmospheric
air is effectively prevented and the engine output is effectively
reduced intensifying the engine brake effect. Subsequently, if the
accelerator pedal is operated to turn the member 8 and
correspondingly increase the throttle opening, the second contact
breaker 214 will initially continue to operate until the slide pin
255 has been moved over a distance corresponding to the partial
length Y of the short circuiting ring 259 and the ignition timing
of the second contact breaker 214 will be advanced by means of the
wire means 226 and connecting rod 222 to approach the ignition
timing of the first contact breaker 215. Subsequently, as the
throttle-valve-operating member 8 continues its turning motion, the
electrode strips 260 and 261 will be separated from the
short-circuiting ring 259, coming into engagement with the rear
nonconducting portion 271 of slide pin 255 extending adjacent to
the short-circuiting ring 259, and thus render the first breaker
215 effective in the place of the second breaker 214. The amount of
ignition advance effected under this switching action is reduced by
an amount corresponding to the advancement of the second breaker
214 previously effected by the connecting rod 222 and associated
means and accordingly, the rapid increase otherwise occurring in
engine power output is relieved.
The above variation of ignition timing is graphically illustrated
in FIG. 13, in which the abscissa represents the r.p.m. of the
engine and the ordinate represents the ignition timing, D denoting
the top dead center. Line 272 represents the spark-advance
characteristic of the first contact breaker 215; line 273
represents the basic spark-advance characteristic of the second
contact breaker 214; and line 273A represents the spark-advance
characteristic of the second breaker 214 in case the connecting rod
222 is drawn to the extreme extent by the accelerator pedal and
thus the second breaker is advanced to the extreme extent. It is
assumed that the device of the invention is put into operation when
the engine is running at low speed with the ignition timing lying
at point a on the characteristic line 273. The timing initially
lying on line 273 will move first to a point on line 273A, such as
a.sub.1, a.sub.2 or a.sub.3 and then to an adjacent point on line
272 or to the very proximity thereto and subsequently onto line
272. Whether point a moves to point a.sub.1, a.sub.2 or a.sub.3 is
determined by the speed of operation of the accelerator pedal. In
case the operating speed is extremely high, the variation in engine
speed during the pedal operation will be negligible and point a
will move, for example, to point a.sub.1. Further, if the device of
the invention is put into operation when the engine is in
high-speed operation with the point of ignition timing lying at
point b on line 273, the point b will first move to a point on line
273A such as b.sub.1 or b.sub.2 and then immediately to a point
c.sub.1 or c.sub.2 on line 272. This increase in spark advance or
the distance between points b.sub.1 and c.sub.1 or between b.sub.2
and c.sub.2 is still appreciable, it is apparently reduced to a
remarkable extent compared with that obtainable if the ignition
timing be varied from point b on the characteristic line 273
directly to a point on line 272 such as point c.sub.1.
With the device according to the invention it will be appreciated
that such marked reduction in variation of ignition timing at the
instant when the second breaker 214 is replaced by the first
breaker 215 realizes substantial reduction in the shock otherwise
exerted upon the engine and its supports.
As has already been described, the first and second contact
breakers 215 and 214 provided for ignition of spark plugs 266 are
switchable between themselves by electric switch 254. The wiring
connection associated with this is schematically illustrated in
FIG. 14.
If the switch 254 is arranged as indicated at 254A in FIG. 17, for
selective connection of the two breakers 215 and 214 to the primary
side 264A of ignition coil 264, the ground circuit including the
primary side 264A will be opened at the instant when the switch
254A is transferred, and spark ignition will be effected at this
instant with an ignition timing differing from that intended and,
depending upon the timing of such premature ignition, misfiring may
occur as described below. For example, in switching over from the
first breaker 215 to the second 214, if ignition is effected upon
operation of the switch 254A immediately before the switching is
actually completed, so-called misfiring tends to occur since,
subsequently when the second breaker 214 acts to interrupt the
primary current of coil 264, the electric charge accumulated in the
time is insufficient to effect actual ignition.
The ignition system schematically shown in FIG. 14 is designed to
overcome the difficulty described above. Referring to FIG. 14, a
parallel arrangement of first and second breakers 215 and 214 is
provided in the primary side 264A of ignition coil 264 with a
switch 254 inserted in the circuit of second breaker 214. As shown,
the first breaker 215 remains connected to the ignition coil 264
when the switch 254 is opened, both breakers being connected to the
ignition coil 264 with the switch closed.
The operation of the system of FIG. 14 will next be described. When
switch 254 is opened to select first breaker 215, spark ignition is
placed under the control of the breaker 215 alone and will be
effected each time the contacts thereof are opened. Such ignition
is shown in the chart of FIG. 15 at point A and the ignition timing
is advanced. Subsequently, when switch 254 is closed, first and
second breakers 215 and 214 are both connected to ignition coils,
as described above, but in this state, ignition is not effected at
the instant when the contacts of first breaker 215 are opened since
the ignition coil 264 is grounded through the second breaker 214 as
long as the contacts thereof are closed and the grounding of coil
264 is broken only when subsequently the contacts of second breaker
214 are opened. Thus, in this case the second breaker 214 is
selected and ignition is effected each time the contacts of second
breaker 214 are opened with a retarded timing as indicated by point
B in FIG. 15.
Though with the arrangement of FIG. 17 spark ignition is made even
at the instant when the switch 254A is operated, as described
hereinbefore, and thus cause various inconveniences, it will be
recognized that such inconveniences can be effectively avoided with
the arrangement of FIG. 14 since opening the switch 254 causes no
spark ignition except when such switch opening is effected by
chance within the desirable range of ignition timing. More
specifically, as long as the contacts of the first breaker 215 are
closed, the ignition coil 264 is grounded through the first breaker
circuit 270 and such grounding is in no way affected by the opening
of switch 254, prohibiting occurrence of any spark ignition with
such switch opening. Similarly, when the contacts of first breaker
215 are open, ignition coil 264 is ungrounded as long as the
contacts of second breaker are open, and under such condition the
opening of switch 254 will exert no effect upon the ungrounded
state of the ignition coil and thus causes no spark ignition. On
the other hand, if the switch 254 is opened when the first breaker
contacts are open with the second breaker contacts remaining
closed, it will be apparent that the grounding of ignition coil 264
is broken to cause spark ignition but such ignition will have no
adverse effect upon engine operation as it is timed intermediate
the point of advanced ignition A and that of retarded ignition B in
FIG. 15.
Again with the arrangement of FIG. 14, there is a danger that
ignition is unduly advanced if the resistance of the circuit of
second breaker 214 be increased, for example, with some damage to
its contacts since in this case the closing of switch 254 causes a
relatively large current to flow through the circuit of first
breaker 215. This apparently means that the opening of the contacts
of first breaker 215 will have a larger influence upon the coil 264
than the opening of the contacts of the second breaker, and spark
ignition will thus be effected each time the contacts of first
breaker 215 are opened.
One arrangement designed to overcome this difficulty is shown in
FIG. 16, in which reference numeral 274 indicates a resistance
element inserted in the first breaker circuit 270 to make the
latter relatively high in resistance in order to avoid passage of
any relatively large current through the first breaker circuit 270
when both breaker circuits are employed. Further, it is desirable
to provide means for bypassing the resistance element 274 when
switch 254 is operated to select the first breaker 215 since
otherwise the resistance 274 will cause loss in power consumption.
In the arrangement shown, the switch 254 is operable between two
switch contact 276A and 276B, and one of these contacts 276B is
inserted in a circuit 275 bypassing the resistance element 274 when
the switch 254 is thrown to select first breaker 215. The other
switch contact 276A is inserted in the second breaker circuit 269,
as shown.
Although several embodiments of the present invention have been
shown and described herein, it will be apparent to those skilled in
the art that many changes and modifications can be made without
departing from the spirit of the invention or from the scope of the
appended claims.
* * * * *