Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INTERNAL COMBUSTION ENGINE F~N DRIVE
An internal combustion engine, such as a diesel engine,
normally includes a cooling fan which is driven by the
engine and moves air through the engine radiator and across
the engine. The purpose, of course, is to prevent the
engine and the accessory parts from overheating. In the
past, such a fan has been connected to be continuously
driven regardless of the engine temperature or speed, but in
more recent years, fan drives including clutches have been
developed for driving the fan only under certain conditions.
For example, the fan would not have to be driven on a cold
day or when the vehicle is moving fast because cooling would
not be necessary or desirable. The purpose of such a fan
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drive is to turn the fan only when cooling is required, and
thereby to conserve engine fuel and to make more power
available to move the vehicle when fan cooling is not needed.
Still another purpose is to reduce fan noise by disengaging
the clutch whenever possible.
A number of fan drive designs have been developed to
fulfill this function. The Geiger U.S. patent No. 2,927,563
discloses a system wherein the engine lubrlcant is utilized
as the actuating fluid, the system including an engine
coolant temperature sensor for operating the clutch. U.S.
- Patent No. 3,804,219 and Borg Warner Corporation Brochure Form
2262-7 R 5M2/76 disclose a drive wherein compressed air is
employed to actuate the clutch.
A disadvantage of drives of the foregoing character is
that they have required three or more fluid connections
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to the drive. In the case of an ~ir pressUre ~ctuated system,
air lines must be connected and hydxaulic lines must be pro~ided
to circulate a lubricant through the dri~e~ In the case of
an engine lubricant pressure actuated clutch, a control line
and two lubricant circulating lines have been provided.
` Another disadvantage lies in the operation of at least
some of the foregoing systems. Pressure is applied to actuate
the clutch by opening a valve, and the pressure is supposed to
~; be released by closing the valve. However, when the valve is
closed, the pressurized 1uid is locked in the clutch and the
pressure drops relatively slowly as the fluid leaks through
the clutch parts. This relatively slow release of pressure
may cause the clutch to operate in a partially engaged condi-
tion, resulting in excessive heating of the clutch plates
`~ and wear and/or glazing of the plates.
Briefly, the present invention seeks to provide an
improved fan drive which avoids the foregoing problems. The
~ drive utilizes the engine lubricant as the control and lubri-
;~ cating medium, and only two fluid connections to the drive are
required. A pressure release valve is provided which is
operated from the lubricant pressure and from centrifugal force.
The invention in its broader aspects pertains to a fan
drive for an internal combustion engine having an engine drive,
a fan, and an engine lubricating system including a pump having
a high pressure outlet and a low pressure return. The fan
drive includes a non-rotatable mounting shaft adapted to be
secured to the engine, a fan hub rotatably mounted on the shaft
and housing means rotatably mounted on the shaft and on the hub.
The housing means includes drive means adapted to be rotatably
driven by the engine and includes clutch means having first
clutch parts attached to the housing means with second clutch
; parts attached to the hub. The first and second clutch parts
are relatively movable between engaged and disengaged positions.
The clutch means further includes a clutch piston mounted within
the housing means adjacent the clutch parts, the housing means
; and the piston form a pressure chamber therebetween with the
chamber being bounded by seals which enable leakage of lubri-
cant from the chamber. A control passage formed in the shaft
is connected to the chamber and is adapted to be connected to
the high pressure outlet. A control valve connected to the
control passage controls the flow of lubricant to the passage
and to the chamber, the control valve having an open position
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where it enables the flo~ o~ lubricant to the chamber and a
closed position where it blocks the flow oE lubricant to and
' from the chamber. Lubricant pressure in the chamber forces
- the piston to engage the first and second clutch parts and
; engage the clutch means, and a pressure-speed responsive valve
is formed on one of the housing means and the piston. The
pressure-speed responsive valve is connected between the
chamber and the low pressure return and is closed to lubricant
flow at high pressure and open to lubricant flow at reduced
pressure.
The foregoing and other aspects and advantages of the
present invention will become more apparent from the following
detailed description taken in conjunction with the accompanying
figures of the drawings, wherein:
Fig. 1 is a side elevational view of an internal combus-
tion engine including a fan drive in accordance with the
present invention;
Fig. 2 is an enlarged sectional view of the fan drive
shown in Fig. l;
Fig. 3 is a fragmentary enlarged view of a valve of the
fan drive, appearing with Figs. 1 and 4; and
Fig. 4 is a view similar to Fig. 3 but showing different
, positions of the parts, appearing with Figs. 1 and 3.
With reference to Figure 1, the reference numeral 10
indicates an engine which may be conventionally constructed
with the exception of the fan drive and the associated control
connections. The engine 10 includes a head 11, a block 12,
an oil pan 13, a turbocharger 14 and a manifold 15. A sheave
17 is connected to be driven by the crankshaft of the engine
10 through an accessory gear train (not shown) and is employed
to drive accessories of the engine including a fan drive 21
(Figs. 1 and 2) in accordance with the present invention.
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The drive 21 is supported by a mounting bracket 22 on
the front end of the engine 10. A plurality of threaded
holes 24 are formed through the bracket 22 for the purpose
of fastening the bracket 22 to a member 20 of the engine
using bolts, for example. On the mounting bracket 22 is
rigidly secured a stationary mounting shaft 26 which extends
~: forwardly from the bracket 22. The shaft 26 is cylindrical,
and the central portion 29 of the shaft, starting at a ledge
indicated by the numeral 28, has a reduced diameter. Further,
the forward one-third portion 31 of the shaft 26 is still
further reduced in diameter starting at another ledge 32.
.
The rearward one third portion of the shaft is indicated by
the numeral 30.
, A hub 36 is rotatably mounted on the forward onethird
portion 31 of the shaft 26 and supports fan blades 35 and
blade carriers 34. The hub 36 includes an internal bore 37
which fits over the portion 31 of the shaft 26, and a needle
bearing 38 rotatably mounts the hub 36 on the shaft 26.
, 20 Between the forward end surface of the shaft 26 and the
central part of the hub 36 are mounted-a number of annular
.
Belleville springs 42 and a roller thrust bearing 43. The
: thrust bearing 43 absorbs the thrust load between the hub 36
: and the shaft 26, and the Belleville springs 42 preload the
bearings. The fan blades 35 and carriers 34 are secured to a
radially extending flange 44 of the hub 36, bolts 46 being
employed to secure the carriers 34 to the hub 36.
- The fan drive 21 further includes a housing including a
sheave part 51 and a cQVer part 52 which are secured together
by a plurality of angularly spaced bolts 53. The sheave
part 51 is rotatably mounted on the rearward portion 30 of
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the shaft 26 by a rear roller bearing 54, and the cover part52 is rotatably mounted on the outer surface of the hub 36
by a forward roller bearing 58. As shown in Figure 2, the
- two bearings 54 and 58 are angled such that the bearing 54
prevents forward movement of the sheave part 51 and the bearing
58 prevents rearward movement of the cover part 52. The
inner race of the rear roller bearing 54 is prevented from
moving forwardly by a retainer ring 62 that is attached by
screws 63 to the shaf~ 26 at the ledge 28, just forwardly
of the bearing 54. The inner race of the forward bearing 58
is prevented from moving rearwardly by a retainer ring 64
that is fastened in an annular groove formed in the outer
periphery of the hub 36, and by a retaining washer 66 that is
located between the bearing 58 and the ring 64. A rear rotating
shaft seal 67 is mounted between the outer surface of the
rearward portion 30 of the shaft 26 and the inner periphery
of the sheave part 51 immediately to the rear of the bearing
54, and another rotating shaft seal 68 is mounted between
the outer periphery of the hub 36 and the inner periphery
of the cover part 52 ~ust forwardly of the bearing 58.
It will be apparent from the foregoing that the
housing is rotatable, due to the bearings 54 and 58, with
respect to the shaft 26 and with respect to the hub 36.
: Further, the shaft seals 67 and 68 prevent leakage of fluid from
the interior of the housing. A pair of annular V-belt re-
ceiving grooves 69 are formed in the outer periphery of the sheave
part 51, the grooves receiving the two belts 18. Consequently,
when the engine is operating, the belts 18 rotate or drive the
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sheave part 51 and the cover part 52.
Since the hub 36 is rotatable both with respect to the
shaft 26 and the housing parts 51 and 52,the hub will not turn
unless a clutch mechanism, indicated generally by the reference
numeral 71, is engaged. The clutch mechanism 71 is mounted in
the enclosure formed by the housing parts 51 and 52, and
.~ includes two or more radial discs 72 which have inwardly extend-
ing tangs 73 formed on their inner periphery. The tangs 73 are
located in angularly spaced slots 74 formed in ~he outer surface
- 10 Of the hub 36, so that the discs 72 rotate wi~h the hub 36. The
clutch mechanism 71 further includes three or more annular
plates 76 which are interleaved with the discs 72. The plates
76 have a plurality of radially outwardly extending tangs 77
which are received in axially extending slots 78 formed in a
~ piston housing 79. The piston housing 79 includes a tubular
f hub 81 which is rotatably mounted on the central part 29 of
the shaft 26, a radially extending rear wall portion 82 which
extends from the hub portion 81 radially outwardly to closely
adjacent the outer wall of the sheave part 51, a tubular
outer wall portion 83 which encloses the plates 76 and the
discs 72 and which has the axial slots 78 formed therein, and
a radially outwardly extending flange 84 which is clamped
between adjoining surfaces of the sheave part 51 and the
cover part 52. A ring 86 is also located between the flange 84
and the cover part 52 to connect the piston housing 79 to the
housing parts 51 and 52. Since the flange 84 is clamped to
. 30 . the housing, it will be apparent that when the housing is
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rotated by the belts 18, the piston housing 79 and the plates
76 will also be rotated.
An axially movable piston 91 is also provided which
serves to actuate the clutch 71. The piston 91 is rotatably
- mounted on the outer surface of the hub 81 of the piston
housing 79, and a seal 92 is provided between the piston 91
and the hub 81. The piston 91 extends radially outwardly
from the hub 81 to closely adjacent the inner periphery of
the outer wall portion 83 of the piston housing 79, and
another seal 93 is provided between the piston 91 and the
: outer wall portion 83. A radially extending pressure surface
' 94 is formed on the forward side of the piston 91 adjacent
- the plates 76. Thus, if the piston 91 were moved forwardly,the plates 76 and the discs 72 would be pressed together
between the surface 94 and a radially extending surface 96 of
, the cover part 52.
The pressure of the lubricant of the lubricating system
of the engine is employed to actuate the clutch. An axially
extending control passage 101 is formed in the shaft 26,
which extends axially forwardly to a location which is
radially aligned with the hub 81 of the piston housing 79.
A radial passage 104 extends from the axial passage 101 to
the outer periphery of the shaft 26, and an annular groove
106 formed in the inner periphery of the hub 81 connects
with the passage 104. A plurality of radially extending
passages 107 are formed through the hub 81 and connect the
groove 106 with a pressure chamber 108 formed between the
forward side of the plston housing 79 and the rear side of
, 30 the piston 91. The chamber 108 is closed at the inner and
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outer ends by the two seals 92 and 93. It will be apparent
that when the passages 101 and 104, the groove 106 and the
chamber 108 are filled with a lubricant under pressure, the
-~ pressure of the lubricant will force the piston 91 and the
rear wall portion 82 of the piston housing 79 apart. Since
the piston housing 79 cannot move axially due to the flange
being clamped, the piston 91 will move forwardly, and the
~ plates 76 and the discs 72 will be pressed together between
; the surfaces 94 and 96. Two additional seals 111 are provided -
between the hub 81 of the piston housing 79 and the shaft 26,
on opposite sides of the groove 106, in order to prevent loss
of pressure in the chambex 108.
In addition to the control passage 101, fluid passages
are also provided in the shaft 26 to carry the lubricant to
the bearings and to the clutch 71 in order to cool and
lubricate them. An axially extending feed passage 112 is
formed through the length of the shaft 26, and another
axially extending return passage 113 is formed from the ledge
28 to the rearward end. The clamping ring 62 has a passage
116 formed therein to permit return flow to the passage 113
; from the interior of the housing. A curved tube scavenger
pump 114 ls connected to the passage 116, which will pump
; the lubricant from the interior of the housing to the passage
113.
The drive is connected to the lubricant system of the
engine by two lengths of hose or tube 121 and 122. The hose
121 is preferably connected in the system adjacent the
pressure or outlet side of the engine driven lubricant pump
(not shown), and the hose 122 is connected to a return line
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leading to the lubricant reservoir. Couplings or fittings 123
secure the hose 121 and 122 to the bracket 22. The hose 121
connects with the feed passage 112 and the hose 122 connects
. with the return passage 113. Thus, engine lubricant will
continuously flow, when the engine and the pump are operating,
into the passage 112, through the bearings and around the
clutch plates, and out of the passage 113.
The control passage 101 is connected to a branch passage
126 ~hich extends from the control passage 101, through a valve
I27 and to the rearward end of the feed passage 112. The valve
i 127 is mounted on the lower end of the bracket 22, and an
electrical solenoid 128 is fastened to and operates the valve
127. Electrical leads 129 connect the solenoid 128 with a
control circuit (not shown~. The control circuit does not form
part of this invention, and may, for example, comprise a
thermostatic switch connected in series with a power supply and
the solenoid 128. The switch may be connected to sense the
engine temperature and be closed at above a given temperature,
and thereby energize the solenoid 128 and open the valve 127.
When the valve 127 is closed, pressure communication
between the feed passage 112 and the control passage 101 is
blocked, and the lubricant flows only through the feed
passage 112, the lubricating and cooling paths in the fan
drive, and the return passage 113. When the valve 127 is
open, the lubricant flows through the above-mentioned lubricat-
ing and cooling paths, and the full lubricant pressure also
appears in the branch passage 126 and in the control
passage 101.
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When the engine 10 is operating and the belts 18
are turning the sheave part 51 and the cover part 52, if the
valve 127 is closed, the pressure in the chamber 108 is low
? and the piston 91 floats in the piston housing 79 and does
~ not force the plates 76 and the discs 72 together. When the
-~ engine temperature rises to above a predetermined level,
:~ the valve 127 is opened and the lubricant pressure in the
chamber 108 will force the piston 91 forwardly or toward the
right as seen in Fig. 2, and the discs 72 and the plates 76
will be compressed between the surfaces 94 and 96. In these
:~ circumstances, the discs and the plates will be essentially
locked together and there will be substantially a direct drive
connection between the sheave part 51 and the hub 36.
The clutch of the fan drive further includes a
pressure release valve 131 for reducing the pressure in the
~: chamber 108 relatively rapidly after the valve 127 has been
~:. closed. While the valve 131 may be formed in either the
"
piston 91 or in the piston housing 79, it is preferably formed
in the radial rear wall 82 of the housing 79. The valve 131
includes a passage 132 (Figs. 3 and 4) formed through the rear
wall 82 of the piston 79, adjacent the outer wall 83. The
passage 132 has a circular cross section and its centerline
extends parallel to the axis of rotation of the piston 79. A
free or unrestrained ball 133 is positioned in the forward
end of the passage 132, and the diameter of the ball 133 is
greater than the diameter of the passage 132. The forward
end of the passage 132 has a tapered seat 134 for the ball,
and an axially extending counter bore 136. The diameter of
the counter bore 136 is substantially greater than that of the
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passage 132, and the tapered seat 134 extends between the
passage 132 and the counter bore 136, As shown in Figs. 3
and 4, the diameter of the counter bore 136 is substantially
larger than the ball 133 so that the ball is free to move
radially in the counter bore. When the ball 133 is seated on
the forward edge of the passage 132 (Fig. 3), the forward side
of the ball is spaced from the piston 91, but it is possible
for the hall to roll radially and forwardly on the tapered
seat to the Fig. 4 position where it engages the piston 91
which holds the ball 133 in the counter bore. In the Fig. 4
position, the ball uncovers the passage 132 but it is still
closely adjacent the forward end of the passage 132.
Assume that the belts 18 are turning the parts 51
and 52, the piston 91 and the piston housing. If the valve
127 is closed and there is no lubricant in the chamber 108
adjacent the valve 131, the centrifugal force acting on the
i ball 133 will move the ball outwardly to the Fig. 4 position
, where it is restrained by the piston 91. When the valve 127
is opened, the lubricant under pressure flows rapidly into the
chamber 108 and starts to flow out of the chamber 108 through
the passage 132. The flow rate of the lubricant out of the
chamber 108 and through the passage 132 quickly increases
until the differential pressure across the ball 133 is
sufficient to overcome the centrifugal force and move the ball
~ 133 against the seat (Fig. 3). The differential force men-
- tioned above arises from the pressure drop across the restricted
flow passage formed between the ball 133 and the seat 134 when
the ball is in the Fig. 4 position. As soon as the ball 33
seats and blocks the passage 132, the pressure builds up in
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the chamber 10~ and engages the clutch, and the lubricantpressure holds the ball on the seat.
When the valve 127 is subsequently closed, the
lubricant in the chamber 108 is momentarily trapped. This
lubricant turns with the parts 79 and 91 and the centrifugal
force exerted by the lubricant on the piston 91 momentarily
holds the piston against the clutch plates and keeps the
clutch engaged. There is however slight leakage of the
lubricant out of the chamber 108 through the seals 92, 93
and 111, and the lubricant pressure in the chamber 108 drops
siightly. There are two forces acting on the ball 133,
the centrifugal force which operates to move the ball radially
outwardly to the Fig. 4 position, and the lubricant force
which operates to hold the ball seated. When the lubricant
pressure drops, the lubricant force falls below the
centrifugal forse, and the ball then moves to the Fig. 4
position. The lubricant then flows through the passage 132
and into the chamber which contains the pump 114, and the
resulting pressure drop in the chamber 108 quickly disengages
the clutch. The lubricant flowing out of the chamber 108 is
replaced by air which moves relatively easily through the
seals.
It will be apparent that a new and useful fan drive
has been provided. While the fan drive includes feed and
return paths through which the lubricant continuously flows,
and also a clutch control path through which lubricant inter-
mittently flows, only two fluid connections to the drive are
necessary. The pressure release valve 131 produces a rapid
drop in lubricant pressure and disengagement of the clutch.
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The valve 131 is very simple in construction and operation,
and it operates automatically without any controls required.
The functioning of the valve 131 is dependent on a
number of factors including drive speed, the ball size and
weight. Those skilled in the art may design the valve,
taking the critical factors into account, to obtain the
operating characteristics desired. The following is an
equation setting out the forces acting on the ball 113:
E 1 F2 -------------------------------(1
A cos~/2 2
Fl = 28.38 W2 Rs (RPM) sin ~9/2 ------------(2
F2 = ~4333 (R M)2 (Rs - Rfl A cos~ /2 -------(3
A = ~d/2 cos A~ / )2 - _ ________________
W2 = 4/3 ~ (d/2 ~ (DB )-4/3 ~ (d~2) (Df)(5
'''
where PE is the lubricant pressure required to seat the ball 133.
Rf is the radius from the axis of rotation of the
shaft 26 to the center of the feed opening 107.
Rs is the radius from the axis of rotation of the
shaft 26 to the centerline of the valve passage 132.
, ~ is the angle of the tapered seat 134 (see Fig. 3).
RPM is the rotational speed of the shaft 26.
A-is the area of the ball 133 within the line of
contact with the seat (Fig. 3).
d is the diameter of the ball 133.
,~ W2 is the effectiYe weight of the ball 133 when in
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the lubxicant.
DB is the density of the ball material.
- Df is the density of the lubricant.
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