Oil bath disc clutch structure

#This invention concerns improvements in oil bath disc clutch construction, particularly the clutches used on chain driven go-carts, mini racing carts or the like as described in detail in U.S. Pat. No. 4,111,291, particularly in the exploded view of FIG. 9 thereof, the entire disclosure of which patent however, is hereby incorporated herein by reference. In the operation of such clutches, multiple releases and re-engagements of the high temperature accommodating friction discs from and with the floater discs thru engine deceleration and acceleration take place within a clutch disc gallery partially filled with oil. in such clutches, each friction disc often comprises a supporting metal disc having angularly spaced friction segments, e.g., 40 or so of friction lining material such as automobile clutch lining. These segments have previously been formed by slotting the lining on each side of the friction disc to a depth of about 0.01 in. and a width of about 0.05 in. These slots which act as oil discharge passages extend completely across the annular contact faces of the disc, typically about 0.4 in.

#It is noted that with such clutches wherein the motor shaft and floater discs are rotating at near clutch engagement speed, the clutch oil is centrifugally slung radially outwardly in the housing to a depth of, e.g., ⅜″ to ½″ to completely immerse the friction segments. In such an environment even at low engine rpm all discs are normally loaded up with oil thru rotation of the floater discs thru the oil sump. Then, as the engine sped is increased and centrifugal forces rotate the cam weights to act on the pressure plate to force the friction and floater discs into engagement, the oil is trapped between the discs and acts as a hydraulic cushion. Even though the cushion dissipates quickly and allows the disc surfaces to forcefully engage each other, the time period required for the dissipation results in variations of, for example, 25%-30% in the engine speed needed to fully engage the clutch. These variations are quite nettlesome to the driver whose performance relies on immediate and anticipated response to his operation of the accelerator. In this regard, hot clutches often throw hot oil out on the driver or can ignite, creating a dangerous situation.

#Additionally, during this time period when the excess oil is being forced out from between the discs, portions of the discs slide on each other and, of course, generate frictional heat, e.g., up to about 280° F. or more. Such heat deteriorates the lining composition of the friction discs and also warps or cracks the floater discs and drastically shortens the clutch life, often before a race is completed.

#The invention will be farther understood from the following description and drawings where certain structures are shown enlarged for clarity and structural proportions vary from figure to figure, and wherein:

#FIG. 1 is a generally axial cross-sectional view of the present clutch in a disengaged condition, taken along the line 1-1 in FIG. 2, with a portion of the motor shaft mounted therein and with portions of the cam weight support broken away and portions thereof shown in relief for clarity;

#FIG. 2 is a view of the cam weight support body taken along line 2-2 of FIG. 1 in the direction of the arrows and showing only one cam recess and one set of eight sets of identical cam weights, the location of the other recesses shown by broken lines;

#Referring to the drawings and with particular reference to the claims hereof, the present clutch construction comprises a housing 10 which contains a first power train section having drive hub means 12 rotatably mounted on a rotation axis 14 in said housing and having bushing means 16 adapted for connection to an output or drive shaft 18 of an engine for rotation thereby, centrifugal cam means 20 mounted on a distal portion 22 of said hub means for rotation therewith, pressure plate means 24 mounted on said cam means for rotation therewith and for axial motion with respect thereto in response to changes in engine speed, said hub means 12 further having axially extending first keying means 26 extending distal 25-to-proximal 27, backing plate means 28 affixed to said hub means proximal to said first keying means and axially spaced from said pressure plate means to provide a substantially closed containment c 30 for a clutch disc gallery at least two annular floater discs 32 having second keying means 33 axially keyed to and slidable along said first keying means 26 between said backing plate means and said pressure plate means for rotation therewith and for axial movement thereon within said housing, each said floater disc having a substantially uniform axial thickness with proximal 34 and distal 36 annular smooth metal contact faces, a second power train section in said housing and having one or more fiction discs 38 mounted over and radially spaced from said first keying means and axially positioned between said floater discs and keyed to said housing 10 as at recesses 40 interiorly of sprocket drum 56 by modes 41 on 38 for axial movement in said housing and for rotation therewith, each said friction disc having an annular metal support 42 of substantially uniform axial thickness providing an annular rim 44 having said nodes 41, a plurality of composition friction segments 46 affixed to each side of said rim and angularly spaced there around by oil discharge slot means 48 to provide a friction face 49, albeit discontinuous, on each side of said rim, said cam means 20 being adapted to axially force said pressure plate means against a clutch gallery of floater discs and friction disc to force said floater discs and friction discs into locking engagement with each other at a predesigned engine speed whereby said housing will be forced to rotate thus its engagement with the rotating friction discs, and power transmission means 50 affixed axially to the exterior of said housing for connection to one or more wheels of a vehicle for driving the same, wherein said oil discharge slots 50 extend from an outer periphery 52 of said friction face thru an inner periphery 54 thereof, wherein said metal faces and said friction faces are in general axial alignment, and wherein the ratio of the total contact surface area (in.2) of a friction face to the total volume (in.3) of the slots in said friction face ranges from about 60 in.2/in.3 to about 100 in.2/in.3.

#It is particularly noted that a test was conducted under actual running conditions employing a test clutch identical to the presently claimed clutch except that the total volume of the test clutch slots measured approximately 0.01 in.3 per side of the friction disc and the floater discs and backing plate were not apertured as claimed by applicant. In the test, the total volume of the slots per side of the presently claimed friction disc measured approximately 0.036 in.3.

#In the test, the temperature within the disc gallery of the test clutch rose to about 280° F., whereas within the disc gallery of the present clutch the temperature did not get above about 200° F.