CA1142044A

CA1142044A - Engine fan clutch

Info

Publication number: CA1142044A
Application number: CA000321337A
Authority: CA
Inventors: Brian C. Deem; Richard J. Reitz
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1978-06-21
Filing date: 1979-02-13
Publication date: 1983-03-01
Also published as: SE7905438L; JPS5825887B2; IT7923709A0; IT1121845B; AU4791379A; GB2023750A; SE443850B; FR2429356B1; DE2924877A1; GB2023750B; FR2429356A1; JPS5527574A; BR7903904A; AU526229B2

Abstract

ENGINE FAN CLUTCH
ABSTRACT OF THE DISCLOSURE
A fan clutch for a vehicle engine connects the engine cooling fan with the engine when the cooling effect of the engine fan is necessary and disconnects the fan when its cooling effect is not necessary. The clutch includes a driven member and a driving member and a belt carried by the driving member and rotatable therewith which is adapted to engage the driven member when the clutch is to be engaged. The driven member comprises a pair of rela-tively rotatable, axially extensible portions so that when the below is in driving engagement with the driven member, relative rotation between the portions extends the same so that engagement surfaces on one of the portions and on the driving member are brought into engagement thus connecting the driven and driving members. A spring, which is responsive to centrifugal forces generated by rotation of the driving member, holds the belt in driving engagement with the driven member when engine speeds are below a predetermined level, but yields to permit the belt to move out of engagement with the driven member when engine speed exceeds the predetermined level. A temperature responsive capsule in-cludes a lever which holds the spring in a position maintaining engagement of the belt with the driven member when the temperature level exceeds a predetermined level, regardless of engine speed.

Description

-This invention re]ates to a clutch of the type which may be used as a fan clutch drive for a vehicle engine.
Because of the high cost of fuel, and because of governmental noise regulations, i~ is desirable to provide a fan clutch which disconnects the engine cooling fan when its cooling effect is not necessary, and which connects the fan for operation by the vehicle engine when the engine temperature rai~es to a point that the cooling effect of the fan is necessary. In many vehicles, the cooling effect of the engine fan is necessary during less than ten per cent of the time that the vehicle is operated.
When the fan is powered when its cooling effect is not necessary, the power necessary to drive the fan is wasted, thereby increasing fuel consumption. ~urthermore, engine cooling fans are inherently noisy, and by disconnecting the fan when it is not necessary, the operating conditions of the vehicle may be quieted. One type of fan clutch which has been highly successful with heavy duty veh~cles having air brakes is the clu~ch disclosed in U.S. Patent No. 3,985,214, owned by assignee of the present invention.
However, this fan clutch design is not compatible with smaller vehicles which do not have air brakes, and whlch are usually provided with direct driven fans. Typical examples of the type of engines in which a fan clutch made pursuant to the teachings of the present invention may be used are trucks having medium-sized gasoline engines or small diesel engines.
The present lnvention resides in a clutch wherein there is provided a pair of relatively rotatable coaxial members including a driving member and a driven member, the driven member including a pair of axially extensible portions responsive to relative rotation between W S /~

the portions to effect ex~ension thereof to drivingly - engage the members. A belt is carried by the driving member and is rotatable therewith for engagement with one of the portions to effect relative rotation between the portions. The belt is responsive to the rotational velocity of the driving member to engage the belt with the one portion.

ThereEore, an important object of our invention is ~o provide a fan clutch for a vehicle engine which permIts additional fuel savings over the fuel savings accomplished by existing fan clutches.
Another important object of our invention is to provide a fan clutch with an idle speed dropout feature which disconnects the fan at a fast idle speed, but which provides a thermostatic con~rol which re-engages the fan if the engine temperature increases above a predetermined level.
Another important object of our invention is to provlde a fan clutch which is smaller and less expensive than existing fan drive clutches.
Another important object of our invention is to provide a fan clutch which provides a one-to-one drive ratio when the clutch is engaged.
Sti~l another important ~object of our invention is to provide a ,fan clutch with improved response time over that in e~isting fa'n clutches.
DESCRIPTION OF THE DR~WINGS
Figure 1 is a front plan view, partly in section~
of the preferred embodiment of a fan clutch made pursuant to the teachings of our present invention; -Figure 2 is a cross-sectional view taken substan-tially along lines 2-2 of Figure 1, with the vehicle ws/?,' fan ~lades shown in phantom;
Figure 3, which appears on-the same sheet of drawings as Figure 1, is a fragmentary vlew, partly in section, taken substantially along lines 3-3 of Figure 2;
Figure 4 is a view similar to Flgure 2 of another èmhodiment of our invention;
. Figure S is a fragmentary view similar to a portion of Figures 2 and 4 illustrating still another important embodiment of our invention; and - Figure 6 is a view similar to Figures 2 and 4 of still another em~odiment of our invention.
. DETAILED DESCRIPTION
Referring now to Figures 1-3 a fan clutch generally indicated by the numeral 10 includes a driving member 12 having a radially extending portion 14 which terminates.
in an axially projecting, circumferentially extending.
section 16. Member 12 also carries an axially projecting spindle 18. Apertures 20 in the radially extending portion 14 are adapted to receive mounting bolts 22 ~o secure th.e driving member 12 to a drive pulley, or directly to the crankshaft of the vehicle engine, so that the driving member 12 will be rotated whenever the vehicle engine is operating. The fan clutch 10 is rotated in the di~ection indicated by the arrow l'A".
. A driven member generally indicated by the numeral 24 is rotatably mounted on the spindle 18 and on a circumferentially extending portion 26 qf ws/

the driving member 12 by bearings 28, 30, respectively.
Conventional ~an blades 32 (shown in phantom in Figure 2) are attached to the driven member 24 by bolts 34 extending into apertures 36 provided on the member 24. The driven member 24 comprises an inner portion 38 which is rotatably mounted by the bearings 28, 30 as discussed hereinabove, and an outer portion 40 which is supported on the outer circumferential surface 42 of the portion 38 and is rotatable relative the~eto.
Circumferentially spaced rollers 44 are mounted for rotation about axles 46 which are held against rotation in bores 48 provided on the outer circumferential surface 42 of the portion 38. Accordingly, it will be noted that the axles 46 project radially from the surface 42. The outer edge 50 of the portion 40 of the member 24 is provided with corresponding tapered recesses 52 which receive the rollers 44, as best illustrated in Figure 3. The recesses 52 are defined by a circumferentially extending, axially tapering camming surface 54. The edge 56 of the portion 40, which is opposite the edge 50, defines an engagement surface which cooperates with a corresponding engagement surface 58 on the radially extending portion 14 of the driving member 12. The surface 58 comprises conventional ` segments of friction material 60, in a manner well known to those skilled in the art to provide a clutch engagement surface.
The outer circumferential surface of the portion 40 generally indicated by the numeral 62 defines a V-groove 64 which is adapted to receive a driving belt 66. Referring now to Figure 1, one end 68 of the belt 66 is attached to the axially projecting section 16 of the driving ~ember 12 by screws 70. The belt 66 wraps around the driven member 24 in a direction opposite to that of the direction of rotation o~
the members indicated by the arrow "A". A spring arm 72 is mounted on a bracket 73 carried by the portion 16 of driving member 12 adjacent the other end 74 of the belt 66, and is ~ pc/,, adapted to deflect radially with respect to the driving member 12, but normally engages the belt 66 to maintain the latter in the groove 64 when the members 12 and 24 are e~ther stationary or rotating at a very low speed as will be discussed hereinafter.
A bracket 76 is also mounted on the section 16 of driving member 12. The bracket 76 pivotally mounts a lever 78 by pivot connection 80.
One end of the lever 78 terminates in a camming surface 82 which is adapted to engage the belt 66 and force the latter into driving engagement with groove 64 as the lever is rotated in the clockwise direction. The opposite end 84 of the lever 78 contacts the plunger 86 of a temperature responsive wax capsule 88. The temperature responsive wax capsule 88 is conventional~
and is responsive to ambient air temperature to extend plunger 86 to pivot the lever about the pivot 80. The wax capsule 88 is yieldably mounted on the bracket 76 by a spring 90, so that the capsule 88 can move relative to the bracket 76 after the plunger moves a predetermined distance. A leaf spring 92 yieldably urges the lever 78 in the counterclockwise direction, to provide a return force on the plunger 86.
_ODE OF OPERATION OF THE PREFERRED EMBODIME~T
When the vehicle engine is operating at a slow idle, operation of the fan is sometimes necessary to provide engine cooling. Accordingly, the spring arm 72 maintains the belt 66 in engagement with the groove 64, thereby causing the portion 40 of the driven member 24 to rotate with the driving member 12, it being noted, as discussed hereinabove, that the driving member 12 will rotate whenever the engine is operating. The resistance of the fan blades 32 causes the portion 38 of the driven member 24 to resist rotation. Accordingly, since the portion 40 is now rotating with the driving member 12, relative rotation will occur between the portions 38 and 40 of the driven member 24, causing the rollers 44 to be forced up the tapered portion 54 of the camming surEace 52. ~s the rollers are forced up the camming surface 54 due to the relative rotation between the portions 38 and 40, the portion 40 will be forced axially relative to the portion 38, toward the driven member 12, thereby causing the engagement surface 56 on the portion 40 to frictionally engage the engagement surface z ~
58 comprising the friction material 60. When this occurs, the driven member 24 is now in dri-ving engagement with the driving member 12, so that the vehicle engine is now turning the fan blades 32 to cool the engine.
~ t some predetermined engine speed, centrifugal force acting on the band 66 due to the fact that it rotates with the driving member 12 yieldably urges the belt in a direction radially outwardly with respect to the members 12 and 24. As engine speed increases, the centrifugal force increases, and at some predetermined engine speed, the centrifugal force generated by rotary movement of the belt is sufficient to overcome the force exerted on the belt by the spring arm 72. When this occurs, the spring arm 72 yeilds, thereby permitting the belt 66 to move radially with respect to the portion 40 to move away from the walls of the V-groove 64.
When this occurs, the driving connection between the driving member 12 and the portion 40 through the belt 66 is broken, permitting the rollers 44 to move back down the camming surface 54. The portion 40 is moved axially with respect to the portion 38 to the left viewing Figure 2, so that the engagement surface 56 moves away from the engagement surface 58, thereby completely breaking the driving connection between the driving and driven members. When this occurs, the only driving connection between blades 32 and the vehicle engine is due to bearing drag, so that only a minimal amount of engine power is wasted driving the fan.
At high engine speeds, if the engine temperature increases sufficiently, the wax capsule 88 reacts, driving the plunger 86 to rotate the lever 78 in the clockwise direction. When this occurs, the lever 78 pivots about the pivot 80, causing the camming surface 82 of the lever 78 to overcome the centrifugal force exerted by the belt 66 rotating with the driving member 12 and thereby urging belt 66 into frictional engagement with the V-groove 64, to re-engage the clutch in the same manner as discussed hereinabove. Accordingly, even at the high engine speed which usually forces the belt into a position overcoming the force of the spring arm 72, the reaction of the wax capsule 88 will re-engage the clutch to cause rotation of the fan. Therefore, the fan will always be engaged whenever eitller of two conditions are satisfied: eitiler the engine is operating at a relatively low speed, or the engine temperature pc/ , ~

;ncreases above som_ predetPrmlned temperature level. It is noted that the clutch mechanism illustrated in Figures 1 to 3 is inherently self-adjusting, because upon disengasement of the clutch, the rollers may be forced only part of the way down .he camming surface 54. This, of course, cornpensate, for i;ear of the friction material 60, so that the degree of axial trave7 required of ~he portion l~o of driv~n mernber 24 rernains substantially constant regardlesi of the width of the friction matelial 60 DETAiLED ~E CR ~ 0~ lF TH~
Referring now to the embod7ment of Figure 4, elernents substantially che same as those in the preferred embodiment ret3in the same referar,ce character, but increased by 100. The embodimen~ of Figure 4 is subs~an~ially the sa,ne as the preferred embodimant, excep~ that the rollers 44, axles 46, and recesses 52 arè replaced by a screw thread generally irldicated by the numeral 192 on the portions 138 and 140 o~ the driven men-ber 124. The lead of the screw threads 192 is at a direction opposi~e the direction of rotation indicated b~t ~he arrow"A", so that the lead oF the ~hr-eads 192 is in the sarne direction of the forcedue to the resistance of the fan blades 132 upon actuation o~ the clutch.
Acc~rdingly, the screw threads give a self--energizing effect to the belt drive and force the powar scre~/ threads, upon relative rotation between the members 138 and 140, into engagerner,t with the engaging surface 158 on the dri~ing mPmber 112~ Again, this design is inherently self-adjusting, since the pc~ er screw threads need only retract a very small amount upon release of the clutch in order to break the driving oonnection.
D 7A LED D SCR~P7 ON OF THE SECOND A rl~N~ ~ EM~3 M~NI
In the emhodimen~ or Figure 5, eler-/Pnts the sam_ as ~hosa in the first al~ernate embodimen~. retain the same reference numerals, but are increased by 100. The embcd-m-slt o, Figure 5 is slmilar co ~he embcldi~ent of Flgure 4, except that an in,:ermediat~ member 294 is installed ~et~.~eer, ~h~ surfaces 25Sand 266. The intermediate member 291~ is s~lined for rot~tion with the member 238, so that the driviny ~orque is transm,it~ed from an~ ,emb2r 2'~ through fntermediate po,t'on 2~4 a~d member 238. In tne absence of intermediate member 294, drivins to.~ue must be transmitted through portion 240, which may be undesirable in some installations.
DETAILE~ DtSCRlPTlON OF THE THIRD_ LTE~NArE _ M~ODI~lErlT
Referring now to the embodiment of Fisu,e 6~ elements subs~antially the same as those in the preferred embodiment ret~irI the same re-~erence character, but incraase by 300. The device illustrated in Figure 6 is subs~antially ,:he same as the preferred embodiment, except Instead of the rollers 4~ aIld camming surfaces 54, circumferentially spaced recesses 396 and 398 are pro~ided in ~he portions 338 and 340 of the driven member 324. Force trar~smitting elements or spheres 400 are disposed in the recesses 396, 398, and are utged up the tapered walls thereof upon relative rotation between the portions 338 and 340, to there-by effect axial separation of ~he portions 338 and 340~ The design of the camming surfaces on the recesses 3~6, 398 is more completely described in U.S~ Patent No. 2,955,6~0. It will also bf noted that a flat belt 366 has been provided in lieu of tlle V bel~ 66 in tt:e preferred embodiment~ A spring (not shown~ similar to the spring 72 in the preferred embodiment is prov;dad to urge ~he belt 366 against member 340. A thermal actuator 388 which may be iden~.ical to the thermal actuator 88 in the preferred embodlment, is moun~ed on the driving member 312, and reacts radially ayalnst the belt 366, to hold the latter and to engage with the outer circumferential surface of the portion 3l:0 when th~
clutch is to be engaged. Appropriate return of springs 402 are pro~/ided to urge the portion 340 to the left viewing the Figure, when the clutch is to be released. When this occurs~ the spheres 400 will fall back into the recesses ~96, ~8.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a clutch, a pair of relatively rotatable coaxial members comprising a driving member and a driven member, said driven member including a pair of axial extensible portions responsive to relative rotation between said portions to effect extension thereof to drivingly engage said members, a belt carried by said driving member and rotatable therewith for engagement with one of said portions to effect relative rotation between said portions, said belt being responsive to the rotation of said driving member to engage said belt with said one portion.

2. The invention of claim 1, and temperature responsive means carried by said driving member for forcing said belt into engagement with said one portion when the temperature level sensed by the temperature responsive means is above a predetermined level and to permit the belt to disengage from the one portion when the temperature level sensed by said temperature responsive means is below a predetermined level.

3. The invention of claim 2, including means resisting the radial outward movement, of the belt due to the rotational velocity thereof and engaging said belt to yieldably urge the latter radially inwardly with respect to said driving member, said last-mentioned means yielding from an initial engaging position in response to pressure thereon due to radial outward movement of the belt in response to centrifugal forces generated by rotation of the driving member above said predetermined level.

4. The invention of claim 3, wherein said means resisting the radial outward movement is a spring arm carried by said driving member.

5. The invention of claim 3, wherein the temperature responsive means includes structure engaging said belt to maintain the latter in engagement with said driven member when the temperature sensed by the temperature responsive means attains the predetermined level.

6. The invention of claim 5, wherein said structure includes a lever pivotally mounted on said driving member having a camming surface engaging said belt and said temperature responsive means includes an expansion member which expands in response to temperature changes to pivot said lever into a condition whereby said camming surface holds said belt against said driven member.

7. The invention of claim 1, including means resisting the radial outward movement of the belt due to rotational velocity thereof and engaging said belt to yieldably urge the latter radially inwardly with respect to said driving member, said last-mentioned means yielding from an initial engaging position in response to pressure thereon due to radial outward movement of the belt in response to centrifugal forces generated by rotation of the driving member.

8. The invention of claim 7, wherein said means responsive to the rotational velocity of the driving member is a spring arm carried by said driving member.

9. The invention of claim 1, wherein one end of said belt is secured to said driving member and said belt wraps around driven member in a direction opposite to the direction of rotation of said driving member.

10. The invention of claim 1, said driven and driving members having complementary, radially projecting, circumferentially extending axial engagement surfaces thereon, and friction material on one of said surfaces, said surfaces being separated axially when the clutch is disengaged and in driving engagement with one another when the clutch is enaged.

11. The invention of claim 1, and camming means interconnecting the portions of said driven member, said camming means being responsive to relative rotation between said portions to effect axial extension thereof.

12. The invention of claim 11, wherein said camming means includes rollers rotatably mounted on one of said portions and a tapered camming surface on the other portion.

13. The invention of claim 12, wherein-said rollers are rotatable about an axis extending radially with respect to said one portion, said camming surface being tapered in a circumferential direction.

14. The invention of claim 11, wherein said camming means includes a recess having tapered walls in at least one of said portions, and force transmitting elements in said recess urged up said tapered walls to effect axial separation of said portions, and return springs yieldably urging said portions toward one another.

15. The invention of claim 11, wherein said camming means is a threaded connection between said portions, the lead of said threads comprising said threaded connection being opposite to the direction of rotation of said members.

16. A clutch comprising a pair of rotatable coaxial members rotatable relative to each other, one of said members being a driving member, the other member being a driven member and being rotatably carried by said driving member, said driven member including an axially fixed portion and an axially movable portion carried by said fixed portion, said driving member including a radially projecting portion defining a friction face and an axially projecting circumferentially extending portion substantially overlying said movable portion of said driven member, said movable portion defining a first friction face opposed to said friction face of said driving member and a second friction surface disposed radially inwardly from said axially extending portion of said driving member, means responsive to relative rotation of said driven member portions-for forcing said axially movable portion and said first friction face in an axial direction to engage the friction face of said driving member, a belt secured at its one end to the axially extending portion of said driving member and extending circumferentially adjacent said second friction surface of said driven member in a direction opposite to the direction of rotation of said driving member and terminating in a free end, said belt defining a friction surface disposed adjacently said friction surface of said driven member axially movable portion, resilient means carried by said driving member and cooperating with said belt adjacent its free end for urging said belt at the friction surface thereof drivingly against said driven member movable portion at the friction surface thereof and resiliently engaging said belt with said driven member when the rotational velocity of said driving member is less than a predetermined value and allowing disengagement of said belt from said driven member when said rotational velocity exceeds a predetermined value, temperature responsive means carried by said driving member and cooperating with said belt adjacent its free end for urging said belt drivingly against said driven member movable portion when the temperature sensed by said temperature responsive means is above a predetermined value and to permit the belt to disengage from said driven member when said sensed temperature is less than a predetermined value.

17. The clutch of claim 16 wherein said means for forcing said axially movable portion against said driving member includes at least one circumferentially extending, axially tapering camming surface formed in one of said portions and a cooperating roller carried by the other of said portions.

18. The clutch of claim 17 wherein said roller is journaled for rotation about a radially extending axis.

19. The clutch of claim 16 wherein said means for forcing said axially movable portion against said driving member includes a screw threaded formed coaxially on one of said portions and a cooperating screw thread formed on the other of said portions, the lead of said cooperating threads being such that when said movable portion is rotated with. respect to said fixed portion in the direction of said driving member rotation said movable portion is forced axially toward said driving member.

20. The clutch of claim 17 wherein said means for forcing said axially movable portion against said driving member includes at least one pair of circumferentially extending cooperating tapered recesses formed in said members.
and a roller disposed in said recesses, the taper of said recesses being such that rotation of said movable portion with respect to said fixed portion in the direction of said driving member rotation causes said movable portion to be moved toward said driving member.

21. The clutch of claim 16, 17 or 18, wherein said temperature responsive means includes a lever pivotally mounted on said driving member having a camming surface engaging said belt and an expansion member which expands in response to temperature increases to pivot said lever into a condition whereby said camming surface holds said belt against said driven member.

22. The clutch of claim 16 wherein said resilient means carried by said driving member includes a spring arm.

23. In a clutch, a pair of relatively rotatable coaxial members comprising a driving member and a driven member, said driven member including a pair of axially extensible portions responsive to relative rotation between said portions to effect extension thereof to drivingly engage said members, a flexible elongate belt having a free end and an attached end, means securing said attached end to said driving member for preventing relative movement between the attached end and said driving member, a friction surface carried by one of said portions for engagement by said belt, yieldable means engaging a section of said belt adjacent the free end thereof to hold said section into frictional engagement with said friction surface, said yieldable means yielding to movement of said section of said belt against said yieldable means due to centrifugal forces on said belt generated by rotation of said driving member above a predetermined speed, the portion of said belt between said section and said attached end flexing in response to relative movement between said section and said attached end when the latter is urged against said friction surface whereby said portion of said belt is also forced into frictional engagement with said friction surface as the clutch is engaged, and temperature responsive means carried by the driving member for engaging said section of said belt to hold the latter in frictional engagement with said friction surface when the temperature sensed by said temperature responsive means is above a predetermined level.

24. The invention of claim 23 wherein said yieldable means is a spring arm carried by said driving member.

25. The invention of claim 23 wherein said belt wraps around the driven member in a direction opposite to the direction of rotation of said driving member.

26. The invention of claim 23 wherein said temperature responsive means includes a lever pivotally mounted on said driving member and an expansion member for pivoting said lever, said expansion member expanding in response to an increase in temperature,

27. The invention of claim 26 wherein said lever carries a camming surface for engagement with said section of the belt.