TRACTION BODY CONSTRUCTION FOR INFINITELY VARIABLE TRANSMISSIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of copending appli¬ cations Serial No. 06/036,232, filed May 4, 1979 and Serial No. 06/077,833, filed September 21, 1979.

BACKGROUND OF THE INVENTION This invention relates to torque transmission apparatus and, more particularly, it concerns improvements in the construction of torque transmitting traction members by which normal force loading for the transmission of torque by friction to or from such members may be supported without objectionable deflection of transmission components. In U.S. Patents No. 4,112,779, No. 4,112,780 and

No. 4,152,946 several continuously variable transmission embodiments are disclosed in which three frame supported working bodies operate to transmit a mechanical power input to a rotatable output at infinitely or continuously variable speed ratios within the design range of the particular transmission embodiment. In the transmissions of this general class, two of the working bodies are in frictional rolling contact with each other at two points of contact as a result of one of the two bodies being of a biconical configuration to define oppositely convergent rolling surfaces of revolution about one axis and the other of the two bodies taking the form of a rotatably coupled pair of rings defining complementary rolling surfaces about another axis inclined with respect to and intersecting the one axis. The rings are adjustable in a manner to vary the radius ratio of the

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contacting rolling surfaces and thus attain the continuously variable speed ratio for which the transmission is primarily intended.

One preferred way of retaining the engaged rolling surfaces in contact under normal force loads adequate to achieve torque transmission by friction has been to provide the biconical body as an assembly of two conical members on ' a common shaft in concentric fashion and to connect the shaft with a cam system operable to forcibly separate the cone members along the axis of the shaft in response to a torque differential between the shaft and the cone members. By coupling the shaft either directly or indirectly to the transmission output load, the force by which the cone member would be urged against the ring-like members could be made proportional to output load. A major difficulty with this approach to normal force development is that the nature and magnitude of the loads imposed on the assembly of cone members and shaft tend to deflect the shaft relative to the cone members causing the cone members to bind or otherwise develop an unwanted path of torque transmission between the shaft and the cone members. The effectiveness of the cam or ramp system operative between the shaft and the cone members is therefore reduced with the result that the normal forces developed at the points of frictional contact are lower than that required to handle the output load of the transmission. This situation, in turn, can result in slippage of the frictionally engaged surfaces, unequal loading at the two points of contact and other factors which reduce efficiency of power transmission and/or cause damage to transmission components. While various solutions to this problem have been proposed and demonstrated to be effective, in retrospec such prior solutions have entailed structural complexity and compromise rather than elimination of potential sources of power transmitting efficiency losses and mechanical failure.

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SUMMARY OF THE INVENTION

In accordance with the present invention, a biconical torque body which includes a pair of cone members subjected to severe diametrically opposite normal force loading is strengthened and rigidified to enable rotational support of the body at opposite ends without measurable deflection or axial misalignment of the rotating and nonrotating parts of each such rotational support. This is achieved by extending the small ends of the cone members to provide bearing shafts integral with the cone members. The shaft extensions of the cone members have a cross-sectional area of sufficient load resisting moment to carry the normal force loading on the body substantially without deflection.

In one embodiment where the cone members are concentric with a central shaft and thrusted in opposite axial directions in response to a torque differential between the shaft and both cones, the bearing shaft extensions of the cones are of annular configuration to accommodate the control shaft. Since the central shaft carries only a small amount of the bending loads imposed on the torq-ue body, the diameter of the central shaft may be reduced to that necessary for handling torque loads only.

In another embodiment the biconical body is con¬ stituted by two oppositely convergent cone members inter- connected without a central shaft at the respective base or large diameter ends thereof for relative rotation and axial displacement with respect to each other. The body is resistant to axial bending as a result of its geometric or biconical

configuration and by transmission of bending stresses through a radial bearing which connects the base ends of the two cones. Also a pilot cone, rigidly connected at its base to the base end of one of the cone members, extends to and is journalled concentrically within the small end of the other of the two cone members and thus further stabilizes the body against .the forces which act thereon.

To develop normal force components by which rolling or traction surfaces on the cone members are pressed into engagement with complementing rolling or traction surfaces of revolution about an axis inclined with respect to and intersecting the axis of the biconical body, the two cone members of the latter embodiment are in axial abutment with each other through complementing cam or ramp surfaces preferably, but not necessarily, located at the concentric small ends of the pilot cone and the other one of the two cone members. The cam or ramp surfaces operate to convert torque acting between the cone members to an axial force or thrust acting to separate the cone members on the axis of . the biconical body. In addition, an adjustable preload force may be imposed on the cone members by a set screw arrangement acting between them.

A principal object of the present invention is, therefore, to reduce to a minimum the deflection of a torque transmitting body of the type referred to and which is supported on its ends by bearings in opposition to diametrica opposed axially spaced normal force loads.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow taken in conjunction with the accompanying drawings in which like parts are designated by like reference numerals.

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BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a longitudinal cross-section of an infinitely variable transmission incorporating one embodiment of the present invention;

Fig. 2 is a longitudinal cross-section through another continuously variable torque transmission incor¬ porating an alternative embodiment of the invention;

Fig. 3 is an enlarged fragmentary cross-section in the same cutting plane as Fig. 2;

Fig. 4 is an enlarged fragmentary section similar to Fig. 3 but illustrating components in a different orienta¬ tion;

Fig. 5 is an exploded side elevation illustrating components shown in Figs. 2-4; and

Fig. 6 is an end view as seen on line 6-6 of Fig. 5.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In Fig. 1, one exemplary embodiment of an infinitel variable transmission unit incorporating the present inventio is generally designated by the reference numeral 10 and shown to include a casing or frame 12 from which working components or bodies of the transmission are supported. In this transmission embodiment, a supporting body 14 is mounted at opposite ends by axle-like extensions 16 and 18 in casing end walls 20 and 22 to be generally concentric with a primary or first ^" axis 24. The extensions 16 and 18 and thus the body 14 are retained against rotation on the axis 24 -by interlocking spline sets 26 and 28, for example. A generally cylindrical body 30 is supported from the extensions 16 and 18 and thus from the frame 12 to be rotatable about the first axis 24 by bearings 32 and 34. The body 30 carries a pair of axially spaced rings 36 and 38 defining internal traction surfaces 40 of revolution about the first axis 24. The rings rotate with the body 30 and are axially adjustable toward and away from each other by appropriate control means such as one or more, preferably three oppositely pitched threaded screws 42 adapted to be driven in rotation on their respective axes by means (not shown) .

A biconical body, generally designated by the ref rence numeral 44, is supported by the body 14 for rotation about a second axis 46 which is inclined with respect to the first axis 24 and intersects the first axis at a point S of axes intersection. Although the body 44 functions as a unit, it is comprised of separate components

in the embodiment of Fig. 1,. such components including a pair of oppositely convergent cone members 48 and 50 defining conical traction surfaces 52 of revolution about the axis 46. The conical surfaces 52 converge at an apex angle which is twice the angle at which the axes 24 and 46 intersect.

In light of this configuration, the traction surfaces 52 on the cones 48 and 50 may be in continuous contact with the traction surfaces 40 on the rings 36 and 38 throughout all axial positions of the rings. Separating the base ends of the conical members 48 and 50 is a ball/ramp assembly 54 including a pair of plate members 56 and 58 biased away from each other under a spring preload developed by a Belleville spring washer set 60. The plates 56 and 58 as well as the base ends of the conical members 48 and 50 are formed having complementing ramp surfaces to engage two pairs of balls 62 and 64 which operate to force the cone members 48 and 50 in opposite directions away from the point S of axes intersection in a manner to be described in more detail below. The conical members 48 and 50 are provided with through-bores 66 and 68 concentric with the axis 46 to fit the external dimensions of a central shaft 70. The shaft 70 includes splines 72 positioned centrally along its length to effect a rotational coupling of the ball/ramp plates 56 and 58 with the shaft 70. Also, the shaft 70 makes a close rotatable and sliding fit at opposite end portions of each of the cone members 48 and 50 in a manner permitting relative rotation and axial movement of the cone members 48 and 50 and the shaft 70. At least .one end of the shaft 70 is keyed with a bevel gear 74 which, in the illustrated embodiment, is in direct meshing engagement with a gear 76 on a shaft 78 journalled in part by a bearing 80 to be independently rotatable with respect to the body 14. A thrust bearing represented by a ball 81 in the drawing is positioned between one end of the shaft 70 and a bracket 82 fixed to the supporting body 14. The opposite end of the shaft 70 is similarly constrained by a washer 83 abutting a portion of

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the body 14. In this way, axial movement o the shaft by reaction to the gears is prevented.

In the embodiment illustrated in Fig. 1, the cylindrical body 30 carries a gear or sprocket 84 by which the body 30 may be driven in rotation about the axis 24.

Although input and output power to and from the transmission may be alternated between the gear 84 and the shaft 78, if it is assumed that the body 30 is driven in rotation by a power input to the gear 84, the driving torque will be transmitted from the traction surfaces 40 by friction to the traction surfaces 52 on the cone members 48 and 50. Torque in the conical members will then be transferred through the balls 62 and 64 to the plates 56 and 58 and to the shaft 70. Torque is then transmitted as output torque to the shaft 78 through the gears 74 and 76.

The torque differential between the conical member 48 and 50 and the shaft 70 is through the balls 62 and 64 which, because of the ramp surfaces in which they are situat will develop an axial separating force on the conical member 48 and 50 proportional to the torque differential. As a result, the traction surfaces 52 on the conical members will be urged into engagement with the traction surfaces 40 under normal force loading proportional to the output load on the shaft 80 in the example given. Because the points PI and P2 of contact between the surfaces 40 and 52 are diametrically opposite from each other, the normal force loading will develop a rocking couple in a direction which, if unopposed, 'would reduce the angle at which the axes 24 and 46 intersect each other. Because the body 14 is fixed in the embodiment under discussion and movement of the biconical body 44 is in simple rotation about the axis 46, the rocking couple is opposed exclusively by bearings 86 and 88 by which opposite ends of the body 44 are supported rotatably in the body 14.

Because of the different moment arms ^' in the rocking couple resulting from normal force loading and the reaction • couple developed by the bearings 86 and 88 there is a tendency for the biconical body 44 and the shaft 70 thereof to be deflected into an S-shaped curve in which the axis 46, when so curved, would intersect the point S and two points centered with the bearings 86 and 88. Such deflection is the result of bending stresses which are substantially equal and opposite along each half-length of the shaft between the respective bearings and the point S.

In accordance with the present invention, deflection in the biconical body 44 between the point S and the bearings 86 and 88 is substantially avoided by providing each of the cone members 48 and 50 with integral shaft extensions 90 and 92 from the small diameter ends of the conical traction surfaces 52. Because the shaft 70 is reduced to a diameter capable of handling exclusively the torque and shear loading on the shaft 70, the shaft extensions 88 and 90 are increased in radial- thickness. Resistance to biconical body deflection as a result of the normal force loading of the traction surfaces 52 is borne entirely by the cone members 48 and 50. Because the conical members are formed of high strength materials of the type used for bearing rollers, and also because of the increased diameter of these members and of the shaft extensions 90 and 92, deflection along the axis 46 is substantially avoided.

The bearings 86 and 88 are preferably hydrodynamic bearings having an inner race defined directly by the shaft extensions 88 and 90 and an outer race or bushing 96 seated in the body 14. The cylindrical interface between the races 94 and 96 is supplied with a lubricant under high pressure supplied by external piping 98 through internal passageways 99 and 100 in the body 14 and the shaft 70, repsectively.

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The facility for the use of hydrodynamic bearings in the support of the biconical body 44 is important not only from the standpoint of accommodating the loads imposed at the gears and the indefinite life characteristics of hydrodynamic bearings, but also, such bearings will enable the necessary slight degree of axial movement in the cone members 52 resulting from elasticity of the material from which the cone members 48 and 50 as well as the rings 36 and 38 are formed. Also, the avoidance of loads on the shaft 70 which tend to cause a relative deflection between the shaft 70 and the cone members 48 and 50 is important from the standpoint of avoiding a direct torque differential between the cone members and the shaft. In particular, any direct transfer of torque from the shaft 70 to the cone members would reduce torque seen by the balls 62 and 64 and reduce the effective normal force loading of the surfaces 40 and 52 to below that which is necessary to transmit a given output torque load on the shaft 80.

In this latter respect, it is to be noted that the bending stresses imposed on the biconical body 44, as a whole, are transmitted to the shaft 70 only at the base ends of the cone members where deflection of the shaft is minimal Also, the moment of direct torque transmission by friction between the shaft and at the inner or base ends of the cone members is small relative to the moment arm of torque transmitted by the balls 62 and 64 and the moment arm of torque transmitted at the traction surfaces 52. Therefore, the magnitude of any unwanted torque differential between the cone members 48 and 50 and the longitudinally central portion of the shaft 70 is small relative to operating torques and required normal force loading which create the unwanted cone-shaft friction forces in this region. Further more, the relative torque arm lengths when the rings 36 and 38 are positioned at the base or large ends of the cone members reduce the effect of the unwanted cone-shaft frictio

because less normal force development by the ball/ramp assembly 54 is needed for the transmission of a given torque, at the base end of the cones than is needed for the trans¬ mission of the same torque at the small ends of the cones. In other words, a lower efficiency of ball/ramp operation can be tolerated under conditions of transmission operation when friction between the central region of the shaft 70 and the cone members is maximum.

At the small ends of the cones, where the arm of the unwanted cone-shaft friction approaches in length, the arm of torque transmission at the traction surfaces 52, the entire reaction to normal force loading on the cone members is borne through the bearings 86 and 88 directly by the cone members and integral shaft extensions 90 and 92. Hence, there is no normal force acting between the shaft extensions and the shaft 70 by which torque can be transmitted by friction between the shaft extensions 92 and 90 and the shaft 70. As a result of this structural organization, the ball/ramp assembly is fully effective to. develop the normal force loading of the cone members against the rings 36 and 38 substantially proportional to the torque load on the shaft 70.

In Fig. 2 of the drawings, an alternative embodi¬ ment of the biconical torque transmitting body of the present invention, generally designated by the reference numeral

110, is shown incorporated in a slightly different continuously variable transmission unit having a frame 112, an input shaft 114 and an output shaft 116. The input shaft 114 is connected as an integral shaft extension with a body 118 supported in the frame 112 by bearings 120 and 122 for rotation about a first axis 124. It will be noted that the body 118 is similar to the body 14 in the transmission of Fig. 1 but, in this instance, is rotatable as a cranking body. The biconical body 110, in turn, is supported directly from the cranking body 118 by bearings 126 and 128 to be rotatable on a second axis 130 inclined with respect to and intersecting the first axis 124 at a point S of axes intersection.

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Supported by and coupled against rotation with respect to the frame 112 are a pair of rings 132 and 134 which are capable of axial adjustment toward and away from the point S of axes intersection. In the embodiment described in Fig. 2, such axial adjustment of the rings 132 and 134 is effecte by one or more oppositely pitched screws 136 rotatable by an external control (not shown) through gears 138 and 140 which are rotatable on axes fixed with respect to the frame 112. An additional control gear 142, rotatable with respect to the frame 112, is shown and in practice is used to synchroni rotation of the gear 140 with corresponding gears for additi sets of double pitched screws (not shown) . A pinion gear 144, connected directly to the biconical body 110 in a manner which will be described in more detail below, meshes with a ring gear 146 coupled directly with the output shaft 116.

Consistent with the several transmission embodimen disclosed in the aforementioned U.S. patents, the biconical body 110 in the illustrated embodiment defines a pair o . -external conical surfaces 148 and 150 of revolution about the axis 130 and which function as rolling or traction surfaces. The surfaces 148 and 150 engage complementing internal traction surfaces on the rings 132 and 134 at two diametrically opposite points of contact PI and P2. As a result of this frictional contact between the biconical body 110 and the rings 132 and 134, the rotational speed of the output shaft 116 in this instance, is the product of both rotation of the cranking body 118 on the first axis 124, causing orbital or planetary movement of the pinion gear 144, and rotation of the pinion gear with the biconical body o

110 on the axis 130. Thus, where α is the rotational o speed of the cranking body 118 about the axis 124; θ is o the speed of rotation in the output shaft 116; ω is the ratio of the traction surface radius on the rings 132 and 134 to the radii of the conical surfaces 148 and 150 at the contact points Pi and P2; and k is the diametric ratio of

the pinion gear 144 to the ring gear 146, the output/input speed ratio of the transmission is determined by the equation: θ/α = 1 - kp. It is to be noted that in the embodiment illustrated in Fig. 2 the biconical member 110 undergoes a nutational movement as a result of its being supported on the second axis 130 by the cranking body 118. In other forms of the same basic transmission and as disclosed in U.S. Patent No. 4,152,946, the biconical body 110 may be concentric with the first axis 124 and coupled directly with an output shaft whereas the rings 132 and 134 are concentric with the second axis 130 and, as such, carried in nutation by the equivalent of the cranking body 1-18. As will be apparent from the description to follow, the structure and function of the biconical body 110 is equally applicable to either form of transmission in this general class.

As may be seen in Fig. 2, the conical surfaces 148 and 150 are the external surfaces of two cone members 152 and 154, respectively. Both cone members 152 and 154 are hollow and extend at their small ends as cylindrical inner race portions 156 and 158 for rotatable support by the respective bearings 126 and 128. Each of the two cones has a relatively large diameter or base end 160, 162 shaped to define telescopic journal formations 164 and 166, which define respectively, outer and inner races of a radial bearing 167. As a result of the journal formations and the bearing 167, the cone members 152 and 154 may rotate relative to each other and also slide longitudinally along the axis 130 in relation to each other. As mentioned above, the pinion gear 144 by which torque is transmitted from the biconical body 110 to a driven load through the output shaft 116 is coupled for rotation with the body 110. In the embodiment under discussion, the sole direct connection of the pinion gear 144 to the body 110 is with the cone member 154. Thus, the gear 144 is formed as an integral extension at the small end of the cone member 154.

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To establish a torque path from the cone member 152 to the pinion gear 144 as well as to stabilize the assembly of the two cones 152 and 154 on the axis 130, the base end 162 of the cone member 154 is secured, such as by welding, to the base end 168 of a pilot cone 170, the small end 172 of which is rotatably and slidably supported by a radial bearing 173 formed between the exterior of the end 172 and the interior of the bearing race portion 156 at the small end of the cone member 152. A cam or ramp assembly 174 operates as the sole torque transmitting coupling between the cone member 152 and the pinion gear 144 through the pilot cone 170 and the cone member 154 in a manner to be described in more detail below.

The cam assembly 174 is located within the bearing race portion 156 at the small end of the cone member 152. As shown most clearly in Figs. 3-6 of the drawings, the assembly 174 includes a thrust plate or plug 176 threadably or otherwise anchored against axial displacement with respect to the cone member 152, a cylindrical cam member 178 coupled by splines 180 for direct rotation with the cone member 152 and a complementing cylindrical cam portion 182 integral with or otherwise nonrotatably fixed at the small end 172 of the pilot cone 170. A set screw 184 is threadably received in the thrust plate 176 and is in abutting relationship with the cam member 178. As may be seen by comparing the illustra tions in Figs. 3 and 4, the splines 180 are of a length sufficient to enable the cam 178 to be adjustably positioned axially in the race portion 156 of the cone member 152 by appropriate adjustment of the set screw 184. As shown in Figs. 5 and 6, cam members 178 and 182 are each provided with complementing annular end camming faces 186 and 188, respectively. These surfaces define a ramp angle by which an angular or rotational force (i.e. torque) is resolved into an axial component of force operatin to separate the cam members 178 and 182 axially. The axial separating force is, therefore, proportional to torque transmitted between the cam members 178 and 182 and the

magnitude of that axial force for a given torque will be determined by the ramp angle of the engaged camming surfaces. 186 and 188. The camming surfaces 186 and 188 are, moreover, bidirectional in the sense that the same axial component of force will be developed irrespective of the relative direction of torque transfer between the cam members 178 and 182.

- - Because of the direct torque path between the cam member 178 and the cone member 152 and between the cam member 182 and the cone member 154 through the pilot cone 170, the torque transmitted by the camming surfaces 186 and 188 will be approximately one half the torque load at the pinion gear 144. The development of this torque and its effect on the operation of the overall transmission in which the biconical body 110 is designed for use will now be explained. As above mentioned, in the operation of the transmission illustrated in Fig. 2, torque transmission from the input shaft 114 and the cranking body 118 to the biconical body 110 is by friction between the rings 132, 134 and the cone members 152, 154 at the two points of contact PI and P2. Assuming that the two points PI and P2 are maintained in symmetry with respect to the point S of axes intersection during operation by appropriate adjustment of the rings 132 and 134, the torque transmitted at the points PI and P2 will be equal, in the same direction and, as such, represent an equal division or splitting of torque delivered to the pinion gear 144. Assuming further that the set screw 184 has been adjusted to preload the conical surfaces 148 and 150 into engagement with the inner surfaces of the rings 132 and 134, no relative movement between the cone members 152 and 154 will occur at torque loads on the output shaft until the normal force required at the point P2 exceeds that developed by the set screw preload. When the torque load on the output shaft 116 exceeds the normal force preload at the point P2, a measure of slippage will occur between the traction surface 150 and the complementing traction surface on the interior of the ring 134. Because the cone member

152 is not connected directly to the pinion gear 144, however the same tendency for slippage will not exist at the point PI except as a result of torque transmitted through the cam assembly 174. Since any torque at the cam assembly 174 will be resolved into an axial separation of the cone members 152 and 154, the normal force development at both points PI and P2 will increase in proportion to the load on the output shaft 116. The magnitude of torque transmitted by the cam assembly 176 will be only one-half the magnitude of the torqu load at the gear 144 because it is the torque carried only by the cone member 152. The magnitude of the axial force component developed by the cam assembly 176, however, and the resulting normal force loading at the contact points PI and P2 will be a function of the ramp angle of the engaged camming surfaces 186 and 188. By design of the ramp angle, therefore, the normal force loading of the conical surfaces 148 and 150 against the rings 132 and 134 may be made proportional to torque loads on the output shaft.

Thus it will be seen that as a result of the present invention, an improved torque transmitting body structure is provided for continuously variable torque transmissions of the type exemplified in the drawings. In both embodiments, the integral extension of the cone members to provide substantially the complete support of the biconica body takes maximum advantage of the biconical geometry of the body as well as the materials used in the cones to resist bending loads imposed on the body. The embodiment of Figs. 2-6 further demonstrates such additional characteristic as simplicity and adaptability of the structure either to a hollow construction as shown or to a solid cone construction at least of the cone 154 and pilot cone 170. This latter characteristic also paves the way to consideration of materials other than high strength bearing alloys for use in the cones, such as less expensive steels and synthetic resinous or plastic materials, particularly in transmissions

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designed for power transmitting capacities which, though lower than the demonstrated power transmitting capacity of existing prototypes of the general class of transmissions under consideration, would have wide application in many fields.

Modifications and/or changes in the illustrated embodime ^' nt are, therefore, contemplated and thus will be apparent to those skilled in the art from the preceding description. Accordingly, it is expressly intended that the foregoing description and accompanying drawing illustrations are of preferred embodiments only, not limiting, and that the true spirit and scope of the present invention be determined by reference to the appended claims.

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