U.S. patent number 3,827,413 [Application Number 05/337,512] was granted by the patent office on 1974-08-06 for timing control system.
This patent grant is currently assigned to Eaton Corporation. Invention is credited to George B. K. Meacham.
United States Patent |
3,827,413 |
Meacham |
August 6, 1974 |
TIMING CONTROL SYSTEM
Abstract
A mechanism for maintaining a predetermined angular phase
relation between a distributing device and a crankshaft in an
internal combustion engine of the type employing an apparatus for
varying the timed angular phase relation between the engine
crankshaft and camshaft. This mechanism, in one disclosed
embodiment, comprises a device drivingly interconnecting the
camshaft and the crankshaft and operative to vary the angular phase
relationship therebetween, a distributor drive gear journaled on
the camshaft, and a spider driving the distributor drive gear in a
constant angular phase relationship with the crankshaft
irrespective of varying phase relationships between the camshaft
and the crankhaft. Several other mechanisms are also disclosed.
Inventors: |
Meacham; George B. K.
(Birmingham, MI) |
Assignee: |
Eaton Corporation (Cleveland,
OH)
|
Family
ID: |
23320840 |
Appl.
No.: |
05/337,512 |
Filed: |
March 2, 1973 |
Current U.S.
Class: |
123/406.11;
123/90.15; 123/90.18; 123/195A; 464/2; 123/406.67; 123/406.73 |
Current CPC
Class: |
F01L
1/34406 (20130101) |
Current International
Class: |
F01L
1/344 (20060101); F02d 037/06 () |
Field of
Search: |
;64/25,24
;123/90.15,90.18,99,117,195A,148R,15R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; Samuel
Assistant Examiner: Heald; Randall
Attorney, Agent or Firm: Teagno & Toddy
Claims
I claim:
1. A timing control system for an internal combustion engine of the
type including at least one cylinder, a piston slideably received
in said cylinder, a camshaft, and a crankshaft drivingly connected
to said camshaft; said timing system comprising:
A. means for sensing engine operating conditions;
B. means responsive to sensed changes in operating conditions of
said engine to selectively vary the angular phase relation of said
camshaft and said crankshaft;
C. gear means carried by and coaxial to said camshaft;
D. a distributing device driven by said gear means for delivering a
charge in a predetermined timed relation to said crankshaft;
and
E. means operative to substantially maintain said predetermined
timed relation between said distributing device and said crankshaft
irrespective of variations in the angular phase relation between
said camshaft and said crankshaft.
2. The timing control system of claim 1, wherein
F. said gear means is journaled on said camshaft.
3. The timing control system of claim 2, wherein
G. said responsive means including a timing gear driven by said
camshaft; and
H. said operative means including a spider drivingly connecting
said gear means to said timing gear.
4. The timing control system of claim 1, wherein
F. said operative means is a linkage system controlled by said
responsive means.
5. The timing control system of claim 4, wherein
G. said responsive means includes a piston member movable in
response to said sensed changes; and
H. said linkage system is controlled by movement of said
piston.
6. The timing control system of claim 5, wherein
I. axial movement of said piston member varies said angular phase
relation between said camshaft and said crankshaft; and
J. said linkage system is responsive to axial movement of said
piston.
7. The timing control system of claim 1, wherein
F. said responsive means is controlled by vacuum pressure from said
engine.
8. The timing control system of claim 7, wherein
G. said vacuum pressure is spark port vacuum pressure.
9. The timing control system of claim 1, wherein
F. said gear means is fixed to rotate with said camshaft, whereby a
variation in the angular phase relation between said camshaft and
said crankshaft produced by said responsive means tends to change
the timed relation between said distributing device and said
crankshaft; and
G. said operative means includes means connected to said
distributing device for imparting a timing compensation to said
distributor counter to said timing change produced by said
responsive means.
10. The timing control system of claim 9, wherein
H. said responsive means includes a piston member movable in
response to said sensed changes; and
I. said connected means imparts said timing compensation in
response to movement of said piston.
11. The timing control system of claim 10, wherein
J. axial movement of said piston member varies said angular phase
relation between said camshaft and said crankshaft.
12. The timing control system of claim 11, wherein
K. said connected means includes a follower for sensing axial
movement of said piston.
13. The timing control system of claim 12, wherein said connected
means further includes
L. a shaft rotated in response to movement of said follower;
and
M. a crank arm operative to impart said timing compensation to said
distributor in response to rotation of said shaft.
14. The timing control system of claim 12, wherein said connected
means further includes
L. a closed hydraulic system having
1. a first cylinder and a first piston defining a first variable
volume fluid chamber, said piston connected to said follower and
operative to vary the volume of said first chamber, and
2. a second cylinder and a second piston defining a second variable
volume fluid chamber in communication with said first chamber, said
second piston connected to said distributing device and operative
to impart said timing compensation to said distributor in response
to variations in the volumes of said chambers.
15. The timing control system of claim 9, wherein
H. said connected means includes motor means operative to impart
said timing compensation to said distributing device in response to
said sensing means sensing changes in said engine operating
conditions.
16. The timing control system of claim 15, wherein
I. said sensing means senses engine vacuum pressure; and
J. said motor means is a timing compensation vacuum motor.
17. The timing control system of claim 16, wherein
K. said engine vacuum is carburetor spark port vacuum.
18. The timing control system of claim 17, wherein
L. said distributing device is an ignition distributor contained in
a housing; and
M. said vacuum motor imparts said timing compensation to said
distributor by rotating said housing.
19. The timing control system of claim 16, wherein
K. said distributing device is an ignition distributor having
1. a housing fixed to said engine, and
2. a movable breaker plate mounted in said housing;
L. a bracket slideably mounting said timing compensation vacuum
motor on said housing;
M. a second vacuum motor fixed to said housing and having
1. a movable wall responsive to said engine vacuum pressure,
2. a control arm secured to one end to said bracket;
N. said timing compensation vacuum motor having
1. a movable wall responsive to said engine vacuum pressure,
2. a control arm secured at one end to said movable wall and at the
other end to said movable breaker plate.
20. A mechanism for maintaining a predetermined angular phase
relation between a distributing device and crankshaft in an
internal combustion engine, said mechanism comprising:
A. a drive pinion driven by said crankshaft;
B. a timing gear driven by said pinion;
C. means driven by said timing gear for driving said camshaft in a
timed angular phase relation to said crankshaft, said means
selectively operable to vary said timed angular phase relation;
D. a distributor drive gear means journaled on said camshaft for
driving said distributing device; and
E. means for driving said distributor drive gear means in said
timed angular phase relation to said crankshaft independent of said
means driven by said timing gear.
21. A mechanism as recited in claim 20, wherein
F. said distributor drive gear means is a spider driven by said
timing gear.
22. A mechanism as recited in claim 20, wherein
F. said gear means includes an antifriction bearing journaling said
camshaft in the housing of said internal combustion engine.
23. A timing control system for an internal combustion engine of
the type including at least one cylinder, a piston slideably
received in said cylinder, a camshaft, and a crankshaft drivingly
connected to said camshaft, said timing system comprising:
A. means for sensing engine operating conditions;
B. means responsive to sensed changes in operating condition of
said engine to selectively vary the angular phase relation of said
camshaft and said crankshaft;
C. a distributing device driven by said camshaft for delivering a
charge in a predetermined timed relation to said camshaft; and
D. means operative to substantially maintain said predetermined
timed relation between said distributing device and said camshaft
irrespective of variations in the angular phase relation between
said camshaft and said crankshaft.
24. The timing control system of claim 23, wherein
E. said responsive means includes a piston member movable in
response to said sensed changes; and
F. said operative means is responsive to movement of said
piston.
25. The timing control system of claim 24, wherein
G. said distributing device is an ignition distributor contained in
a housing.
26. The timing control system of claim 25, wherein said operative
means comprises:
H. a bracket mounted on said engine;
I. a shaft journaled on said bracket;
J. a follower having one end fixed to said shaft and the other end
in sliding contact with said piston, whereby movement of said
piston rotates said shaft;
K. a first crank arm fixed at one end to said shaft for pivotal
movement in response to rotation of said shaft;
L. a second crank arm fixed at one end to said housing of said
distributing device; and
M. a linkage connecting the free end of said first crank arm to the
free end of said second crank arm for rotating said housing in
response to said pivotal movement of said first crank arm.
27. A device as recited in claim 25, in which said operative means
comprises:
A. a crank arm fixed at one end to said distributor housing;
B. a first cylinder;
C. a piston in said first cylinder;
D. an end wall fixed to said first cylinder, said first cylinder,
piston and end wall defining a first fluid chamber;
E. a control arm fixed at one end to said piston and at the other
end pivotally connected to the free end of said crank arm;
F. a second cylinder;
G. a second piston in said second cylinder;
H. a second end wall fixed to said second cylinder, said second
cylinder, second piston, and second end wall defining a second
fluid chamber;
I. a follower adjacent to and in sliding contact with said movable
piston;
J. a rod fixed at one end to said piston and at the other to said
follower;
K. a conduit communicating said first fluid chamber with said
second fluid chamber; and
L. resilient means in said first cylinder for urging said piston to
a position minimizing the volume of said first fluid chamber and
maximizing the volume of said second fluid chamber.
28. The timing control system of claim 23, wherein
E. said sensing means senses engine vacuum pressure;
F. said responsive means varies said angular phase relation between
said camshaft and said crankshaft in response to changes in said
engine vacuum pressure whereby variations in said angular phase
relation produced by said responsive means tend to change the timed
relation between said crankshaft and said distributing device;
and
G. said operative means is responsive to changes in said engine
vacuum pressure, and imparts a timing compensation to said
distributor counter to said timing change produced by said
responsive means.
29. The timing control system of claim 23, wherein
E. said distributing device is an ignition distributor contained in
a housing;
F. said operative means includes a vacuum motor having
1. a housing,
2. a movable wall,
3. a vacuum chamber defined by said housing and movable wall,
4. a control arm secured to said movable wall at one end, and
pivotally connected to said distributor housing at the other end,
and
5. means communicating engine vacuum pressure to said chamber.
30. The timing control system of claim 29, wherein
G. said engine vacuum pressure is carburetor spark port vacuum
pressure.
31. An internal combustion engine comprising:
A. a crankshaft;
B. a camshaft;
C. driven means drivingly connecting said crankshaft to said
camshaft, said driven means selectively operative to vary the
angular phase relation between said camshaft and said
crankshaft;
D. a gear means carried by and coaxial to said camshaft;
E. means defining at least one cylinder having a piston slideably
received therein and drivingly connected to said crankshaft;
F. distributor means drivingly connected to said gear means in
timed relation to said crankshaft and selectively operative to
deliver a charge to said at least one cylinder in a timed relation
to said piston; and
G. means for substantially maintaining said timed relation between
said distributor means and said piston when said driven means is
selectively operated to vary said angular phase relation between
said crankshaft and said camshaft.
Description
FIELD OF THE INVENTION
This invention relates to internal combustion engines and, more
particularly, to timing control systems for use with internal
combustion engines.
BACKGROUND OF THE INVENTION
There is presently a great deal of concern about air pollution,
much of which is said to be contributed by exhaust gases from
internal combustion piston engines. Great effort has been expended
in search of methods for controlling the level of noxious emissions
from such engines. One concept found to be effective for such
control, and at the same time compatible with the contemporary
design of such engines, is explained in detail in U.S. Pat. No.
3,714,932, "Emissions Control System" and U.S. Pat. No. 3,626,720,
"Emission Control Device."
While the concept disclosed in the mentioned applications is
effective in substantially reducing noxious exhaust gas emissions
by selectively varying the angular phase relation of the camshaft
with respect to the crankshaft, it creates a problem with ignition
timing in engines having camshaft mounted distributor drive gears.
Specifically, the camshaft phase change creates an ignition timing
change of a magnitude and direction equal to the camshaft phase
change. This timing change produces undesirous combustion
characteristics and less than optimum control of noxious exhaust
gas emissions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
timing control system for an internal combustion engine.
A more specific object is to provide, in an internal combustion
engine of the type including a crankshaft, a camshaft, and a
camshaft driven distributing device, a timing control system which
optimizes combustion characteristics and control of noxious exhaust
gas emissions.
These objects are accomplished according to the present invention
by the provision of a timing control system in which the angular
phase relationship between the crankshaft and the camshaft is
selectively varied in response to a sensed engine operating
condition, whereby to provide combustion characteristics which
minimize noxious emissions, and in which further means are provided
to maintain the predetermined angular phase relationship between
the crankshaft and the camshaft driven distributor device
irrespective of the variations in the angular phase relationship
between the crankshaft and the camshaft, whereby to further improve
the emission characteristics by maintaining optimum distributor
timing.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a fragmentary elevational view, partially in section,
illustrating one embodiment of the invention timing control system
employing a distributor drive gear journaled on a camshaft;
FIG. 2 is a sectional view, taken along line 2--2 of FIG. 1;
FIG. 3 is a fragmentary elevational view, partially in section,
illustrating a second embodiment of the invention timing control
system employing mechanical linkage;
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3;
FIG. 5 is a fragmentary view, partially in section, illustrating a
third embodiment of the invention timing control system employing
fluid displacement cylinders;
FIG. 6 is a fragmentary view, partially in section, illustrating a
fourth embodiment of the invention timing control system employing
vacuum operated motors;
FIG. 7 is an elevational view in reduced size illustrating a fifth
embodiment of the invention timing control system which also
employs vacuum operated motors; and
FIG. 8 is a partially sectioned view, taken along the line 8--8 of
FIG. 7.
DETAILED DESCRIPTION OF FIGS. 1, 2 EMBODIMENT
FIG. 1 illustrates a fragment of an engine block 10 having a front
wall portion 10a, a crankshaft 12, a camshaft 14, a drive gear
assembly 16, and a camshaft angular phase change mechanism 18
drivingly interconnecting camshaft 14 and drive gear assembly 16 to
the crankshaft.
Crankshaft 12 is schematically shown journaled in an antifriction
bearing 19 supported within an aperture 20 in wall 10a. A timing
pinion 22 is secured to the forward end of crankshaft 12. A
ring-shaped camshaft timing gear 24 is drivingly connected to
pinion 22 via a timing chain 26.
Drive gear assembly 16 is substantially sleeve-shaped and includes
an ignition distributor drive gear 16a having a plurality of
helical gear teeth 16b, an antifriction bearing surface 16c, a hub
portion 16d, a smooth cylindrical bore 16e, and an annular recess
16f at the leftward end of bore 16e. Bearing surface 16c is
journaled within a sleeve bearing 28 supported in an aperture 30 in
wall 10a. Gear teeth 16b are adapted to drive an ignition
distributor pinion (not shown).
Camshaft 14 is rotatably supported within bore 16e of drive gear
assembly 16 via a journal portion 14a formed on the forward end of
the camshaft. An annular rib portion 14b formed on the leftward end
of journal portion 14a mates with recess 16f and provides a
leftward stop for seating drive gear 16 in the axial direction. The
forwardmost part of journal portion 14 extends through bore 16e and
defines a hub portion 14c which is adapted to support phase change
mechanism 18.
Camshaft phase change mechanism 18 when operated functions to
change the angular phase relationship between crankshaft 12 and
camshaft 14. A more detailed description of mechanism 18 may be
found in U.S. Pat. No. 3,626,720. Phase change mechanism 18
includes a piston 32 and a driven member 34, the latter being
nonrotatably secured to hub portion 14c of the camshaft.
Driven member 34 includes a disk portion 34a, a hollow rearwardly
extending hub portion 34b, and a hollow forwardly extending hub
portion 34c. Hub portion 34b is adapted to fit snugly over hub
portion 14c, and is secured thereto against axial movement by a
bolt 36 and against rotational movement by dowels 38.
Piston 32 includes a disk portion 32a, a hollow hub portion 32b,
and an annular rim portion 32c. Hub portion 32b is rotationally and
slideably received within the hollow of hub portion 34c and sealed
therebetween by an O-ring seal 35. Disk portion 34a and hub portion
34c combine with disk portion 32a and rim portion 32c to define an
annular chamber 40 having a helical ball spline device 42 disposed
therein.
The helical ball spline device 42 includes an annular outer race 44
securely fixed to disk 34a and an annular inner race 46
circumscribed by outer race 44 and securely fixed to disk 32a. An
outer circumferential surface 44a of outer race 44 is rotationally
and slideably received within a cylindrical bore defined by an
inner surface 32d of annular rim 32c and sealed therebetween by an
O-ring seal 47. The inner periphery of outer race 44 is provided
with a plurality of straight circumferentially spaced slots 44b.
Slots 44b extend substantially parallel to the axis of camshaft 14
and are disposed adjacent similar circumferentially spaced and
angularly extending slots 46a formed in the outer periphery of
inner race 46. Each corresponding pair of slots 44b, 46a is
provided with a spherical ball 48 therein for drivingly
interconnecting slots 44b and 46a, and hence, providing relative
rotation between piston 32 and drive member 34 in response to axial
movement of piston 32 relative to driven member 34.
Piston 32 is drivingly engaged to timing gear 24 by a plurality of
straight splines 32e formed on the outer periphery of rim portion
32c. Splines 32e engage similar straight splines 24a formed on a
portion of the inner periphery of camshaft timing gear 24. The
other inner peripheral portion of timing gear 24 is rotationally
received about the outer peripheral edge of disk portion 34a and is
held axially secure thereto by a snap ring 50 and the butt ends of
splines 24a.
Drive gear assembly 16 is drivingly connected to timing gear 24 via
an oval shaped spider 52, as shown in FIG's. 1 and 2. Spider 52 is
formed from sheet metal and is freely received within a gap defined
by the axially facing ends of hubs 16d and 34b. A centrally located
aperture 52a in spider 52 freely receives hub portion 14c of
camshaft 14. Spider 52 is secured to timing gear 24 by screws 56
and to hub 16d of drive gear 16 by dowel pins 58.
A servo valve assembly 60, disposed within hollow hub portion 32b,
provides means for admitting pressurized engine oil to chamber 40
or to drain oil therefrom for the purpose of axially shifting
piston 32. The hollow of hub portion 32b is provided with stepped
bores 32f and 32g. An extension of bolt 36 defines a shaft 36a
which is slideably and rotatably received in bore 32f; sealing
therebetween is provided by an O-ring seal 62. Bore 32g is provided
with an annular groove 64 which is supplied with engine oil from a
passage 66 in wall portion 10a via a plurality of intermediate
passages. Specifically, passage 66 extends through bearing 28 and
terminates in an annular groove 68 formed in the periphery of
bearing surface 16c of drive gear assembly 16. Groove 68
communicates with a plurality of radially extending passages 70
which terminate in an annular groove 72 formed in the peripheral
surface of journal portion 14a of camshaft 14. Groove 72
communicates through a radially extending passage 74 with an
axially extending passage 76, which in turn communicates with
groove 64 via passages 78, 80 in driven member 34 and hub portion
32b respectively. Bore 32g is provided with a second annular groove
82 which is axially spaced from groove 64 by an annular land 84.
Annular groove 82 communicates with chamber 40 via a passage
86.
A shiftable spool valve 88 is provided to control oil flow into or
from chamber 40. Spool 88 is slideably positioned within bore 32g
in surrounding relation to shaft 36a and is provided with a pair of
annular grooves 88a, 88b which are separated by a land 88c in
slideable sealing engagement with bore 32g. A wave spring 90
lightly biases spool 88 to the right and a snap ring 92 limits
rightward movement of spool 88 within bore 32g. A drain passage 94
communicates groove 88b with an appropriate sump for return of oil
to the engine.
Spool valve 88 is maintained in a desired position by a control arm
96. Control arm 96 is a rigid structure which includes a forked end
portion 96a positioned adjacent the rightward end of the spool
valve, a handle 96b, and a pivot shaft 96c. Pivot shaft 96c is
rotatably secured in a block 98 which is secured to a wall portion
100 of a cover assembly (not shown) enclosing the mechanisms
extending beyond the front wall 10a of engine 10.
The cover assembly is secured to wall 10a. Handle 96b extends
through wall portion 100 of the cover assembly and is controlled by
an appropriate control system which responds to certain engine
operation conditions which produce high concentrations of noxious
exhaust emissions. One such servo control system using engine
vacuum is disclosed in the aforementioned U.S. Pat. No. 3,626,720.
Testing has shown the such operating conditions are discernable by
the measure of carburetor spark port vacuum, engine speed, or
engine torque.
OPERATION OF FIGS. 1, 2 EMBODIMENT
During one mode of engine operation camshaft phase change mechanism
18 is in the position shown in FIG. 1, i.e., piston 32 is fully
retracted and chamber 40 is a minimum in volume. In this mode of
operation control arm 96 is fully rotated clockwise about pivot
shaft 96c and land 88c is blocking oil communication between
grooves 64, 84 via groove 88a. When an engine operating condition
arises which makes it advantageous to vary the angular phase
relationship between the camshaft and the crankshaft, control arm
96 is rotated counterclockwise about pivot shaft 96c; this allows
spool valve 88 to shift rightward under the force of wave spring
90, thereby communicating grooves 64, 88 via groove 88a and
allowing pressurized engine oil to flow into chamber 40. Piston 32
will thus shift rightwardly under the oil pressure to the position
shown by broken line 102 or any position intermediate as determined
by the amount of servo valve movement allowed by control arm 96.
The rightward movement of piston 32 causes piston 32 to rotate
relative to driven member 34 due to the aforedescribed spline
arrangement in helical spline device 42 and, hence, the angular
phase relationship between crankshaft 12 and camshaft 14 is
changed.
However, as may be seen, this angular phase change between piston
32 and driven member 34 is entirely independent of the phase
relationship between timing gear 24 and drive gear 16 since spider
52 provides the driving connection between timing gear 24 and drive
gear 16. Therefore, drive gear 16 remains in a constant phase
relationship with crankshaft 12 irrespective of the phase
relationship between crankshaft 12 and camshaft 14.
DETAILED DESCRIPTION OF FIGS. 3, 4 EMBODIMENT
FIG's. 3 and 4 schematically illustrate another embodiment of the
invention. In this embodiment like components have the same
numerals used to designate corresponding parts in the previous
embodiment but a suffix "A" is added thereto. Succeeding
embodiments will follow this procedure using consecutive upper case
suffixes. In this embodiment spider 52 is omitted and the camshaft
drive gear is fixed to rotate with the camshaft. Other than this
the angular phase change mechanism is identical in structure and
operation to the mechanism of FIG's. 1 and 2. In this embodiment a
mechanical linkage system 104 is provided to compensate for
distributor timing changes that are transmitted to a distributor
106 as a result of camshaft angular phase changes relative to the
crankshaft, and a distributor drive gear 108a is carried by and
driven by a camshaft 108.
The distributor 106 includes a head assembly 110, a mounting stand
112. The distributor 106 departs from standard distributors in that
the head assembly 110 is rotatable relative to the mounting stand
112. A lower portion 112a of the mounting stand 112 is received by
an aperture 114a in a wall portion 114 of an engine block. A
radially extending flange 112b formed on mounting stand 112 limits
the depth of reception of the lower portion 112a into the aperture
114a and provides means for securely fixing the position of the
stand relative to the wall portion 112, as shown, by bolt 116 and
clip 118.
The distributor head 110 and stand 112 have coaxial openings 120
and 122, respectively, in which rotatably receive a distributor
drive shaft 124. A pinion 124a secured to the lower end of shaft
124 meshes with camshaft drive gear 108a. The upper end of the
shaft 124 extends through a centrally positioned clearance hole
126a in a breaker point mounting plate 126. A breaker point cam
124b formed on upper end of shaft 124, or otherwise secured
thereto, functions to open and close a set of breaker points 128
mounted on plate 126 in a well known manner.
An upper axial end face 112c of the stand 112 serves as a bearing
surface for a lower face 110a of the head 110. A spring 130 is
disposed between two outwardly extending arms 110b and 112d which
are integrally formed with head 110 and stand 112, respectively, as
best shown in FIG. 4. The spring 130 biases head assembly 110
downward and counterclockwise as viewed in FIG's 3 and 4.
The mechanical linkage system 104 responds to axial movement of
piston 32A of phase change mechanism 18A and rotates head assembly
110 to correct for angular phase changes transmitted to breaker
point cam 124b when the phase change mechanism shifts the angular
phase relationship between the crankshaft and the camshaft. Linkage
system 104 includes a pivot shaft 132, a crank arm 134, a pin 136,
and a radially outwardly extending arm 110c formed integrally with
head assembly 110. Pivot shaft 132 includes a vertical rod portion
132a journaled in a pair of blocks 138 and a follower portion 132b
which rides on the face of piston 32A. Blocks 138 are supported on
an appropriate bracket 140 secured to the engine in a conventional
manner. The top end of rod 132a is securely fixed to one end of
crank arm 134. The other end of crank arm 134 is securely fixed to
the lower end of pin 136. An elongate slot 110d formed in the free
end of arm 110c loosely receives a necked down portion at the top
end of pin 136.
The above embodiment has been described and shown schematically for
ease of understanding but it should be realized that in actual
practice each engine model and installation will require slight
design changes in the linkage configuration due to peculiarities
that are inherent in different engine models and installations. For
example, the arms 134 and 110c may be separated by a substantial
distance in which case a push-pull rod or a flex cable may be used
in lieu of pin 136 to transmit the timing compensation signal from
the camshaft angular phase change mechanism 18A to the distributor
head assembly 110. Further, head assembly 110 and mounting stand
112 may be unitary in construction (as are standard distributors)
with rotation occurring in the aperture 114a.
OPERATION OF FIGS. 3, 4 EMBODIMENT
When the piston 32A moves axially to the left (FIG. 3), the
distributor compensation mechanism will operate due to rotation of
the follower 132b and thereby cause the crank arm 134 to rotate.
Rotation of crank arm 134 is transmitted into rotatory movement of
distributor head assembly 110 via pin 136, and arm 110c.
As may be seen, the amount of distributor head rotation depends on
the amount of axial movement of the piston 32A which is
proportional to the amount of camshaft phase change. In tests using
camshaft advance to reduce exhaust emission, it has been found that
a one-to-one compensation (i.e. for each degree of camshaft
advance, the compensation system retards the distributor one degree
to maintain ignition timing in phase with the crankshaft) results
in the best performance for most engines and at the same time
produces the best control of emissions. However, on some types of
engines compensation of less than or more than one-to-one produces
the best results. Of course the ratio of compensation is
controllable by varying the length of follower 132b and/or crank
arms 134 and 110c.
DETAILED DESCRIPTION OF FIG. 5 EMBODIMENT
FIG. 5 is a third embodiment which schematically illustrates a
variation of the compensation means shown in FIG's. 3 and 4. The
angular phase change mechanism 18B and the distributor 106B are
substantially the same as disclosed in FIG's. 3 and 4. In this
embodiment a closed hydraulic system 150 is used in lieu of the
mechanical linkage system of FIG's. 3 and 4.
Closed hydraulic system 150 includes two cylinder assemblies 152,
154 which define interconnected chambers 156, 158 of variable
volume. Chamber 156 is defined by a cylinder wall 160, an end wall
162, and a piston 164. Cylinder assembly 152 is secured to the
engine by a bracket 165 in a conventional manner. Piston 164 is
connected to a follower 166 via a piston rod 168 which passes
freely through an opening in an end wall 170 at the other end of
cylinder wall 160. Chamber 158 is defined by a cylinder wall 172,
an end wall 174, and a piston 176. Cylinder assembly 154 is secured
to stand 112B of distributor 106B via a bracket 177 in a
conventional manner. Piston 176 is pivotally connected to the free
end of an arm 178 via a piston rod 180 which passes freely through
an opening in an end wall 182 at the other end of cylinder wall
172. Arm 178 is a radially outwardly extending portion of head
assembly 110B and is functionally equivalent to arm 110c in FIG's.
3 and 4. A spring 184 interposed between piston 176 and end wall
182 biases piston 176 to the left. Chambers 156, 158 are
interconnected by a conduit 186.
OPERATION OF FIG. 5 EMBODIMENT
When piston 32B is retracted the volume of chamber 158 will be at a
minimum due to the action of spring 184 which biases piston 176
leftward. This leftward biasing of piston 176 forces the hydraulic
fluid from chamber 158 to chamber 156 via conduit 186 and causes
piston 164 to move rightwardly, thereby holding follower 166 into
sliding contact with piston 32B. When an engine operating condition
arises that calls for a camshaft angular phase change the phase
change mechanism 18B is operated and piston 32B moves axially to
left, thereby moving piston 164 leftward and forcing fluid from
chamber 152 into chamber 158; this causes piston 176 to move
against the force of spring 184, thereby rotating head assembly
110B via rod 180 and arm 178.
DETAILED DESCRIPTION OF FIG. 6 EMBODIMENT
FIG. 6 is a fourth embodiment of the invention which schematically
illustrates a vacuum operated compensation system 190. The angular
phase change mechanism 18C and the distributor 106C are
substantially the same as disclosed in FIG's. 3 and 4. Operation of
the compensation means in FIG's. 3, 4 and 5 is responsive to axial
movement of piston 32. In this embodiment the spark port vacuum
signal described in connection with FIG's. 1 and 2 is used to
provide both servo valve control and distributor compensation
control.
Vacuum operated compensation system 190 includes two vacuum motors
192, 194 which are parallel connected to a spark port vacuum
conduit 196 via conduits 198, 200, respectively. Vacuum motor 192
includes housing members 202 and 204, a spring 206, a flexible wall
208 and a control rod 210 which freely extends through an opening
in housing member 204. Control rod 210 includes a fork shaped end
portion 211 which is biased into sliding contact with servo valve
88C by spring 206. Conduit 198 communicates with a vacuum chamber
212 defined by housing member 202 and flexible wall 208. Vacuum
motor 194 includes housing members 213 and 214, a spring 215, a
flexible wall 216, and a control rod 217. Control rod 217 is
pivotally connected to the free end of arm 178C, as described with
reference to the FIG. 5 embodiment. Conduit 200 communicates with a
vacuum chamber 218 defined by housing member 213 and flexible wall
216.
Conduit 196 may be in constant communication with the spark port
vacuum chamber of the engine carburetor, whereby the vacuum signal
will be applied to chambers 212 and 218 whenever the engine is
running, or a valve (not shown) may be installed in conduit 196 to
block or allow application of the vacuum signal to chambers 212 and
218 on demand; the valve may be responsive to engine temperature,
engine speed and/or engine torque. In the disclosed embodiment the
vacuum signal is applied constantly to chambers 212 and 218.
OPERATION OF FIG. 6 EMBODIMENT
Springs 206 and 215 when fully expanded in their respective
chambers are preloaded to prevent movement of the flexible walls
until the spark port vacuum reaches a predetermined amount which
corresponds to an engine operating condition known to produce high
concentration of noxious exhaust. When this predetermined amount of
vacuum is exceeded flexible walls 208 and 216 and their respective
control rods shift to the left by an amount proportional to the
amount of vacuum in excess of the predetermined amount. Leftward
movement of control rod 210 allows servo 88 (FIG. 1) to shift under
the bias of wave spring 90, thereby admitting pressurized engine
oil to chamber 40 and thus varying the angular phase relationship
between the crankshaft and the camshaft. Since the vacuum is also
applied to chamber 218, distributor head assembly 110C is rotated
enough to compensate for the amount of change between the camshaft
and the crankshaft.
DETAILED DESCRIPTION OF FIGS. 7, 8 EMBODIMENT
In this embodiment, the servo valve of the camshaft angular phase
change mechanism may be controlled by a vacuum motor such as shown
in FIG. 6.
FIG. 7 illustrates a distributor installation comprising a
distributor 220, a wall portion 222 of an engine (not shown), and a
camshaft 224 with a camshaft driven distributor drive gear 226. The
distributor drive gear 226 is fixed to rotate with the crankshaft
and, therefore, imparts a timing change to the distributor,
relative to the crankshaft, whenever the camshaft phase is changed
relative to the crankshaft phase.
With reference to FIG. 8, the distributor 220 comprises a housing
228, a breaker plate 230, a breaker point assembly 232 mounted on
plate 230, a breaker point cam 233 driven by distributor drive gear
226, a vacuum motor 234 for timing compensation due to a camshaft
angular phase change, and a vacuum motor 236 for normal vacuum
control of ignition timing as is well known in the art.
The vacuum motor 234 comprises housing members 238 and 240, a
flexible wall 242 (which in combination with the member 238 forms a
vacuum chamber 244), a spring 246, a conduit 248 for communicating
a vacuum to the chamber 244, a bracket 250 for movably mounting the
vacuum motor 234 to the distributor 220 via slots 252 and 254 which
slide on screws 256 and 258, and a control arm 260 for rotating the
breaker plate 230 in response to movement of the flexible wall
242.
The vacuum motor 236 comprises housing members 262 and 264, a
flexible wall 266 (which in combination with the member 262 forms a
vacuum chamber 268), a spring 270, a conduit 272 for communicating
a vacuum to chamber 268, a bracket 274 for securing the motor 236
to the housing 228 in a fixed position, and a control arm 276 for
linear movement in the bracket 250 in response to movement of the
flexible wall 266.
Conduits 248 and 272 are parallel connected and in constant
communication with the spark port vacuum chamber in the same manner
conduits 198 and 200 are connected in FIG. 6.
OPERATION OF FIGS. 7, 8 EMBODIMENT
The inner connection between the normal vacuum control motor 234
and the timing compensation motor 232 maintains ignition timing in
a predetermined relation with the crankshaft by superposition,
i.e., the sum of the movement of control arms 260 and 274 determine
the ignition timing for any particular operating condition.
When spark port vacuum is very low in chamber 268 spring 270 biases
diaphragm 266 rightwardly against housing member 624 with a
predetermined force; this position of diaphragm 266 corresponds to
full retardation of the vacuum advance motor 236. When diaphragm
266 is against housing member 624, the right end of slots 252 and
254 of bracket 250 are biased against screws 256 and 258,
respectively. In a like manner, when spark port vacuum is very low
in chamber 244 spring 246 biases diaphragm 242 against housing
member 240 with a predetermined force; in this position there is no
timing compensation nor is there an angular phase change between
the crankshaft and the camshaft since the phase change mechanism is
also controlled by spark port vacuum. Low spark port vacuum occurs
when the engine is idling, due to the relative positions of the
throttle and the spark port, and during high engine load
conditions.
As the vacuum in chamber 268 increases diaphragm 266 is pulled to
the right against the force of spring 270, whereby control arm 276
pulls bracket 250 and vacuum motor 234 to the right relative to
distributor 220. Since the biasing force of springs 246 and 270 is
greater than the rotational resistance of the breaker plate
rightward movement of motor 234 shifts control arm 260 rightward
and rotates breaker plate 230 counterclockwise to advance the
ignition timing.
As the vacuum in chamber 234 increases diaphragm 244 is pulled
leftwardly against the biasing force of spring 246, thereby
rotating breaker plate 230 clockwise to retard the timing an amount
proportional to the ignition timing advance caused by the phase
change mechanism.
The several embodiments of the invention has been disclosed for
illustrative purposes. The following claims are intended to cover
the inventive portions of the disclosed embodiments and variations
or modification within the spirit of the invention.
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