Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Specification
This invention relates to vacuum pumps and, more
par.ticularly, to a vehicle engine mounted vacuum pump arrange-
mel~t to provide a source of vacuum for driving vacuum motors
and actuators in vehicles having engines, such as diesel
engines, which do not otherwise provide a ready or adequate
vacuum source.
The development of diesel engines for optional use
in place of conventional gasoline engines as prime movers in
automotive passenger cars and trucks has brought a need for
provision of a suitable source of vacuum for operating
vehicle mountea accessories having vacuum motors and actuators
which are normally arranged to operate from the vacuum
developed in the intake manifold of the conventional gasoline
engine.
The present invention provides a diesel engine
mounted vacuum pump arrangement capable of acting as a vacuum
source for driving such vehicle accessories and arranged to be
mounted and make use of drive provisions within the engine
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which are equivalent to means for driving the distributor of
a comparable model of gasoline fueled engine.
The arrangement includes a reciprocating piston
pump having novel features to provide high efficiency with
low noise output. Means for mounting and driving the pump
are also included which take up and distribute internal engine
lubricant for lubricating the drive mechanism and pump pushrod.
These and other features of the invention will be
more fully understood from the following description of a
preferred embodiment taken together with the accompanying
drawings in which: -
Figure 1 is a fragmentary cross-sectional view of
a diesel engine incorporating a vacuum pump and drive means
in accordance with the invention;
Figure 2 is a partial cross-sectional view taken
in the planes indicated by the line 2-2 of Figure 1 and
showing portions of the pump drive and lubrication system;
Figure 3 is a cross-sectional view of the pump and
drive assemblies shown in Figures 1 and 2 taken in the plane
of the line 3-3 of Figure 2 as viewed in the direction of the
arrows;
Figure 4 is a fragmentary cross-sectional view of
the drive arrangement as viewed from the plane of the line
4-4 of Figure 3;
Figure 5 is a fragmentary cross-sectional view of
the lower end of the pump drive housing with the shaft and
gear removed as seen from the plane indicated by the line 5-5
of Figure 3 looking in the direction of the arrows; and
Figure 6 is a bottom view from the plane indicated
by the line 6-6 of Figure 3 showing the lower end of the drive
housing and shaft arrangement with the gear removed.
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Referring now to the drawings in detail, numeral
10 generally indicates an internal combustion engine of the
automotive diesel type having a general arrangement like that
o~ the engine disclosed in United States Patent 4,054,108
e!ntitled "Internal Combustion Engine," issued October 18,
1977 in the name of Lloyd T. Gill and assigned to the
assignee of the present invention.
Engine 10 includes an engine block 11 rotatably
supporting a crankshaft 12 which in turn drives, through
conventional means not shown, a camshaft 14 supported in
bearings 15 within the enclosed portion of the crankcase
defined by the engine block. Oil passages 16, 18 in the
block and camshaft, respectively, form a part of the engine
pressure lubricating oil system used to lubricate the cam-
shaft bearings and other internal moving parts of the engine.
Near one end of the engine block 11 there is
mounted a vacuum pump and drive assembly 20 formed according
to the invention and adapted to provide a source of vacuum
for operating the various vacuum motors and actuators utilized
in a vehicle in which the engine may be mounted. The use of
a separate pump for this purpose is required, since a diesel
engine of the type disclosed does not generate any significant
amount of vacuum in operation and thus does not provide a
significant source of vacuum, as do comparable throttled spark
ignition engines for which the present diesel engine might be
an optional replacement. Pump and drive assembly 20 is actu-
ally made up of two separable components, a pump assembly 21
and a mounting and drive assembly 22 which supports and drives
the pump.
The construction of the pump assembly 21 is best
shown in the cross-sectional view of Figure 3. The pump
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includes a die cast alumlnum base 2~ defining a piston cavity
25 and having a nose portion 26 with a pressed-in hollow
bushing 27 which traps a pushrod seal 28. Reciprocably
carr.ied in the base 24 is a piston assembly including a die
caqt aluminum piston member 29 carrying a rolling diaphragm
type seal 30 and a combination diaphragm retainer and spring
seat 32, all of which are retained together by a pushrod
member 33 which extends through the piston diaphragm and
retainer members and the hollow bushing 27 to the exterior of
the base 24.
A cover member 34 is crimped to the edges of the .
base 24, engaging and retaining the rolling seal 30 in posi-
tion. The cover also encloses the piston assembly and retains
a coil spring 36 which engages the cover 34 and the retainer
and spring seat member 32, biasing the piston assembly toward
the piston cavity 25 of the base 24.
The base 24 and cover 34 together define a housing
forming an enclosure which the piston assembly 29, 30, 32, 33
divides into a first or primary pumping chamber 37 and a dis-
20 charge chamber or second pumping chamber 3g. The pistonassembly reciprocates within the enclosure, varying the
volumes of chambers 37 and 38 in inverse fashion. The clear-
ance volume (least volume) of the primary pumping chamber is
made as small as possible by arranging for a very limited
clearance to exist between the piston member 29 with its
associated rolling seal 30 and the base 24 when the pi~ton is
in its retracted position, the furthest leftward posiLion as
shown in Figure 3. The clearance volume (least volume) of
the discharge chamber 38 is not nearly so small, since this
chamber provides additional volume for retaining the spring.36,
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as well as other clearance increasing features resulting from
the design of the piston, retainer and cover members.
The passage of air, or other vacuum fluid, through
th~ pump follows a path through an inlet connector tube 40
molmted in the base 24 and inlet ports 41 through the base to
the primary pumping chamber 37. From this chamber, the con-
tinued flow is through transfer ports 42 in piston 29 to an
annular recess 44 under the diaphragm and thence through
openings 45 provided in the central portlon of the diaphragm
and openings 46 in the retainer member 32 to the discharge
chamber 38. From the discharge chamber, the fluid passes
through discharge ports 47 provided in a central recessed
portion 48 of the cover member 34 and out between indenta-
tions 49 in a protective baffle member 50 and the surrounding
walls of the cover recess to the exterior of the pump.
The direction of airflow through the pump, upon
reciprocation of the piston assembly, is determined by three
check valves, 52, 53 and 54, mounted respectively in the
base 24, piston 29 and cover 34 and controlling airflow
through the inlet ports 41, transfer ports 42 and discharge
ports 47, respectively. These valves allow fluid flow only
in the direction above described and not in the opposite
direction. Thus, reciprocation of the pump piston assembly
by suitable drive means to be subsequently described causes
the pump to operate in the following manner.
An extending movement of piston member 29 to the
right from the position shown in Figure 3 increases the
volume of the primary pumping chamber 37, drawing air from
the inlet tube into the primary pumping chamber and reducing
the pressure so as to create a vacuum in the primary chamber,
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as well as in the inlet tube and other enclosed chambers to
which it may be attached. At the same time, the volume of
the discharge chamber 38 is being reduced, forcing any air
therein out the discharge openings 47 to the exterior of the
pump. Check valve 53 remains closed during this movement,
preventing reverse flow from chamber 38 to chamber 37.
The return ~retracting) stroke of the piston, from
its furthest rightward position to the position shown in
Figure 3, again increases the volume of chamber 38, while
reducing to its minimum the volume of chamber 37. This move-
ment thus reduces the pressure of the remaining fluid in
chamber 38, check valve 54 closing automaticall~ to prevent
the backfl.ow of atmospheric air into this chamber. At the .
same time, the pressure in chamber 37 increases, closing the
inlet.valve 52. The increasing air pressure in chamber 37
and the reducing air pressure in chamber 38 open check valve
53, and most of the air in chamber 37 passes through the
transfer ports 42 to chamber 38 as chamber 37 approaches and
reaches its least volume. Continuation of pump operation
with another extending movement of the piston member causes a
repetition of the process by drawing another fresh charge of
air into chamber 37 and forcing the residual charge from
chamber 38, as previously described.
It should be noted that the pump assembly 21 would .
~ operate to create vacuum in the desired manner without the
: presence of the cover mounted check valve 54, since an extend- ~*
ing movement of the piston would draw air into the chamber 37
through the inlet ports and a retracting movement of the
piston would force this air out of chamber 37 through the
transfer ports 42, which is all that is necessary to provide
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normal vacuum pump operation. The small clearance volume of
the chamber 37 is, of course, intentionally provided to obtain
a high pumping efficiency for this primary pumping chamber.
The result of this design is, however, that the discharge of
~ir from the primary pumping chamber 37 through the transfer
ports 42 and past the valve 53, diaphragm 30 and retainer
member 32 creates a substantial noise which it is desirable to
suppress. This could, no doubt, be accomplished by providing
some sort of sound suppressing chamber or filter at the outlet
of the pump.
The present invention, however, accomplishes the
desired purpose in a manner which gives an additional added
benefit. This result is obtained by the use of the third
check valve 54, mounted in the cover member and controlling
airflow and the passage of noise through the discharge ports
47. The use of this valve greatly reduces the observable
noise level of the pump, apparently due to the fact that this
valve closes the discharge ports 47 during the period of air
discharge through the transfer ports 42, which creates the
major noise problem. Thus, the sound is effectively muffled
by b'eing enclosed within chamber 38, which is not opened to
atmosphere until after the end of the air transfer step when
the piston begins to extend (move rightwardly) and force air
out of chamber 38 to atmosphere. 'This latter-pumping step is
accompanied by a much lower level of noise than the transfer
step, and thus the overall transmitted noise level of the
` pump is reduced by the presence of the check valve 54. One
~; possible reason for the reduced noise level of the latter
s` pumping step is that the much greater clearance aeast) volume
of chamber 38 than that of chamber 37 does not create the same
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kind of abrupt and rapid outflaw of gas through the discharge
ports 47 that is apparently created in the transfer ports 42
by the movement of the piston to the least volume position of
chamber 37.
Besides accomplishing a substantial reduction of
radiated noise level, the provision of the cover mounted third
check valve 54 also has the effect of irnproving the output
efficiency of the vacuum pump by providing, in effect, a
second stage of pumping operation. Thus, even though the
chamber 38 is not designed with su~iciently close clearance
to reach the pumping efficiency level of the primary pumping
chamber 37, the effectiveness of discharge of air from cham-
ber 37 through the transfer ports 42 is increased by the fact
that chamber 38 is at the same time reduced in pressure, due
to the presence of valve 54 which prevents the entry of
atmospheric air into chamber 37 during retraction of the pump
piston. Thus, by the addition of valve 54, overall pump
efficiency is somewhat increased through the provision of a
second stage of pumping action, while at the same time the
noise transmission from the pump is reduced.
-~ Turning now to the mounting and drive assembly 22,
its functions are to mount the pump, to provide reciprocating
- drive for the pushrod of the pump piston and to provide itself
and the pump pushrod with adequate lubrication. The assembly
22 comprises an aluminum drive housing 56 having a vertical
;~ bore 57 and a pair of spaced needle bearings 58 rotatably
supporting in the housing a drive shaft 60. An eccentric cam
61 is fixed on the upper end of the drive shaft and a drive
gear 62 is fixed on its lower end.
: 30 Drive housing 56 is seated at its lower end in a
. tubular opening 64 provided in an upper wall of the engine
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block. A flat 65 provided on the protruding portion of the
housing forms a lip 66 that is engaged by a clamp 68 held by
a bolt 69 to retain the housing and pump assembly in the
block. The arrangement is the same as retention means used
for the distributor of a comparable gasoline engine, except
that the narrow lip provided by the flat 65 locate~ the
assembly in a relatively fixed orientation on its axis with-
out permitting the rotational adjustment usually provided in
distributor mountings.
At its upper end, the pump base 24 and drive housing
56 are secured together by bolts 70 secured in abutting
portions of the two members, thereby holding the nose portion
26 of the pump base within a recess 72 provided in the enlarged
upper end 73 of the drive housing 56. An o-ring seal 74 is
provided to prevent oil leakage through the joint. The pump
pushrod 33 extends through an opening within the recess 72 into
the upper end of the drive housing where its end is urged by
the pump spring 36 into engagement with the outer race of a
cam bearing assembly 76 mounted on the eccentric cam 61. An
end plug 77 and o-ring seal 78 close the upper end of the drive
housing ahove the cam 61.
At the lower end of the drive housing, the gear 62
extends within the engine block into driving engagement with
; gear teeth 80 formed on the engine camshaft 14 so as to pro-
'~ vide a rotational drive for the gear 62 and drive shaft 60.
The bottom end of gear 62 seats against a thrust pad 81 in
- the engine block which takes the downward thrust generated
between the camshaft and driveshaft gears. In its lower end,
the gear 62 has a hexagonal opening 82 in which is received a
hexagonal driveshaft 84 that extends downwardly into the engine
block to drive the engine oil pump, not shown. This drive
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is accomplished in the same manner as is the oil pump drive
in comparable gasoline engines.
Lubrication of the vacuum pump pushrod and the
pump drive mechanism is accomplished as follows. Within
the engine block there is provided a pipe plug 85 closing
the end of one of the engine oil galleries, not shown, and
having a central orifice 86 through which a spray of pres-
surized oil is delivered against a conical upper surface 88
of the gear 62 located directly above the gear teeth. Some
of this oil is carried downwardly by gravity to lubricate the
engaging teeth of the camshaft and pump gears. However, the
bottom end of the drive housing 56 is provided with a down-
ward protrusion 89 which extends into close proximity with
the conical surface 88 in the quadrant of the gear immediately
beyond the point of impingement of the oil spray thereon.
Protrusion 89 has a trough-like cutout 90 which co-oper~tes
with a conical surface 92 closely appxoaching the conical gear
surface to scoop some of the oil off the surface of the gear
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and lead it upwardly in a spiral motion to the outer surface
of the drive shaft 60 that extends upwardly through the drive
housing bore 57. The outer surface of the drive shaft is
provided with double lead helical grooves 93 which, because of
the close fit of the drive shaft within the bore 57 and bearings
58, act like a screw pump and move oil upwardly in the drive
housing to the eccentric cam 61 mounted on its upper end. Here,
the oil is thrown outwardly, lubricating the cam bearing 76 and
the pump pushrod 73 in its bushing 26, the seal 28 preventing
lubricating oil from being carried into the air passing
through the vacuum pump. A return flow passage 94 is provided
down the center of the drive shaft 60 by which excess oil is
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drained from the upper part o~ the drive housing to the
interior oE gear 62 from which it leaks out to the engine
crankcase through the clearance around the hexagonal drive
shaft 84 or through the grooves 93 in the pump drive shaft 60.
In operation of the drive assembly, rotation of the
camshaft 14 counterclockwise, as seen in Figure 2, causes
rotation of the drive gear 62 and the pump shaft, thereby
rotating the eccentric 61 and causing the outer race of the
bearing assembly 76 to act in conjunction with the spring 36
of the pump to reciprocate the pushrod and piston assembly
of the vacuum pump. This results in the efficient low noise
vacuum pumping action described previously with respect to
the vacuum pump assembly while, at the same time, lubrication
of the rotating and reciprocating parts is provided in the
manner just described.
While the invention has been described by reference
to a preferred embodiment, it should be recognized that
numerous changes might be made within the scope of the inven-
tive concepts disclosed. Accordingly, it is intended that the '
invention not be limited, except in accordance with the lan-
guage of the following claims.
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