Note: Descriptions are shown in the official language in which they were submitted.
~L~3732~3
This invention relates to apparatus for controlling ignition
timing of an internal combustion engine by m0ans of a vacuum response
device having a first vacuum chamb~r for mo~ng an element in one direction
to advance the spark timing, and having another vacuum chamber for moving
the same element in the other direction to retard the spark timing.
Apparatus of this general type requires that one vacuum chamber be subjected
to engine intake vacuum while the other is vented to atmosphere, and vice
versa. In conventional practice this has been accomplished by employing
two three-way control valves, one for each vacuum chamber, together with
apparatus for coordinating their operationO Such a system has been found
to be objectionably large in si~e, relatively complicated as a whole, and
consequently expensive.
An important object of this invention is to provide spark timing
control apparatus for an internal combustion engine, which apparatus connects
engine intake vacuum pressure to either side of a vacuum response member,
.... .
but which is free of the disadvantages described above and which uses only
one three-way control valve instead of two~ The three-way valve is
electrically operated in accordance with speed of a vehicle driven by the ~ ~`
engine. The valve serves to connect engine intake vacuum pressure to
either one of two vacuum chambers formed on opposite sides of a flexible
diaphragm arranged to advance or retard the spark timing~ At the time
either one of the vacuum chambers is connected to engine intake va~uum `~
pressure, the atmospheric vent is closed, and the other vacuum chamber
is connected to atmosphere throug-h a restricted orifice. ~n addition, a
temperature sensitive valve closes at low temperature to cut off the supply ;
of engine intake vacuum pressure to the three-way control valve.
Other objects and advantages will appear hereinafter.
The drawing is in schematic fo~n, partly in section, and shows
a preferred embodiment of this invention.
Referring to the drawing~ the internal combustion spark ignition
engine is provided with a carburetor generally designated 10 having
~k ''`
.. .
.. . ..
~ 37 32~ '
int~lce passages 11 and 12 controlled by throttlc valves 13 and 14~ respec~-
ively. A vacuum conduit 15 conml~uicates with the en~ine :intake passage 11
downstream from the throttle valve 13 through the restriction opening 16.
A spark timing control device generally designated 18 includes a point base
19 mounted to turn about the axis of the rotary point cam 20 which is driven
by the engine. A vacuum response member comprises a slide rod 22 ha~ing
a fork member ~ixed thereto and arranged to move a pin 24 fixed to the point
base 19~ so that movement of the slide rod 22 toward the right, as shown in
the drawing, causes the point base 19 to turn in a clockwise direction to
advance the spark timing. Movement of the slide rod 22 toward the left
serves to retard the spark timing.
A vacuum actuator 26 has a housing 27 divided into a first vacuum
chamber 28 and a second vacuum chamber 29 by means of the flexible diaphragm
30. The outer peripheral portion of the flexible diaphragm 30 is fixed to
the stationary housing 277 and the central portion of the flexible diaphragm
30 is fixed with respect to the slide rod 22. A flexible bellows 31 forms
the inner portion of the first vacuum chamber 28 and serves to prevent
leakage.
The three-way control valve generally designated 32 is ;
electrically operated and contains a solenoid coil 33 whichg when energized,
causes the movable a~mature 34 to move toward the right, as shown in the
drawing, against the action of the coil compression spring 35~ When the `~
armature 34 is moved to the right, the vacu~lm conduit 15 is connected to the
second vacuum chamber 29 through line 37. When the armature 34 returns to
the left under force of the spring 35 upon de-activation of the solenoid
coil 33, the ~acuum conduit 15 is connected to the first vacuum chamber 28
and through the line 38. When the movable armature 34 is in the left-hand
position shown in the drawing, the valve head closes the conduit 3? and
connects the vacuum conduit 15 to the conduit 38. When the valve head 39
is in the right-hand position, the conduit 38 is closed, and the vacuum
conduit 15 is connected to conduit 37.
_ 2 _
~ . . .
'
~L~9373Z~9
A vent valve assembly generally desi.grlated 40 :include~ a housing
41 divided into a first chamber 42 and a. second chamber 43 by m~ans of a
flexible diaphra~m 44 carrying a centrally positioned valve head ~5. A
first vent tube 46 has a restricted opening 47 and serves to conneet the
first ehamber 42 to atmosphere through filter 48. Similarly~ the second
vent tube 49 has a restricted opening 50 and serves to connect the second
chamber 43 to atmosphere through the filter 51. The first chamber 42 is
connected to the first vacuum chamber 28 by means of the conduit 52~ and
the second chamber 43 is connected to the second vacuum chamber 29 through
the conduit 53.
When the first vacuum chamber 28 is subjected to vacuum pressure
through the three way control valve 32 and conduit 38 this vacuum pressure
is applied to the first chamber 42 and causes the flexible diaphragm 44
to move the valve head 45 to close the first vent tube 46. At the same
time the second vacuum chamber 29 is vented to atmosphere through conduit
53, second vent tube 49 and restricted opening 50~ Similarly, when the
second vacuum chamber 29 is subjected to vacuum pressure through the
three-way control valve 28 and conduit 37, the flexible diaphragm 44 causes ~ -
the valve head 45 to close the second vent tube 49. At that time the first
vacuum chamber 28 is vented to atmosphere through conduit 52~ ~irst vent
tube 46 and restricted opening 47~ The vacuum restriction 16 is larger
than the restricted openings 47 and 50.
A temperature sensitive valve assembly 55 is mounted in the
vacuam conduit 15 and acts to close the conduit whenever the ambient
temperature falls below a predetermined level. A bimetal element 56 moves
a valve head 57 to close against valve seat 58 at such low temperatures.
this cuts off the supply of vacuum pressure to the three-way control valve
32, and hence to either of the vacuum chambers 28 or 29. In this situation,
the vacuum response member 22 is returned to neutral position by the action
of the coil springs 59 and 60.
,, ,
3~1~
In operation, when the vehicle speed is relatively high and the
vehicle speed switch 61 is open, and the ignition switch 62 is closed, the
three-way control valve 22 acts to connect intake vacuum pressure to the f:i-rst
vacuum chamber 28. This causes the slide rod 22 to move to the right to
advance the spark timing. The second vacuum chamber 29 is vented to atmos-
phere through conduit 53, second chamber 43, vent tube 48 and restricted open-
ing 50. At the same time, the first vacuum chamber 28 is also connected to
atmosphere through restricted opening 47, and therefore a small quantity of
atmospheric air flows into the first vacuum chamber 28 through conduit 52, but
the quantity is too small to have any substantial effect. When the vehicle
speed falls below a predetermined value, the switch 61 closes, and this causes
the three-way control valve 32 to supply engine intake vacuum pressure to the
second vacuum chamber 29. The first vacuum chamber 28 is vented to atmosphere
through conduit 52 and restricted opening 47. This causes the slide rod 22
to be moved toward the left to retard the spark timingO At the same time,
atmospheric air flows through the restricted opening 50 and conduit 53 into
the second vacuum chamber 29, but the quantity is too small to have any sub-
stantial effect.
Having fully described my invention, it is to be understood that I
am not to be limited to the details herein set forth, but that my invention
is of the full scope o the appended claims.
~ 4 _
:, ' ` ' '
