FR2471522A1 - FRICTION TRANSMISSION MECHANISM - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A FRICTIONAL TRANSMISSION MECHANISM. THIS MECHANISM FEATURES A DRIVING SHAFT LINKED TO A ROTATING CAM-SHAPED BODY AND A BEARING BEARING WITH AN EXTERNAL BEARING BUSH AND AN ELASTICALLY DEFORMABLE INTERNAL BEARING BUSH WHICH PRESS AGAINST THE ROTARY BODY AND AN OUTPUT SHAFT WHICH IS ELASTICALLY DEFORMABLE. CONNECTION WITH A HOLLOW INTERNAL CYLINDER ARRANGED CONCENTRICALLY TO THE EXTERNAL BEARING BUSH AND RESIDING AGAINST IT. THE INTERNAL CYLINDER 11 IS DEFORMABLE AND, CONCENTRICALLY THEREFORE, IS PROVIDED WITH A HOLLOW EXTERNAL CYLINDER 12, DEFORMABLE AND NON-ROTATING RESTING AGAINST THE OUTER SURFACE OF THE INTERNAL CYLINDER SUCH AS THE INTERNAL CYLINDER 11 IS PRESSED CAM IN THE ZONE ROTARY BODY 3 AGAINST THE EXTERNAL CYLINDER 12. A FRICTION GEAR IS ALSO OBTAINED FOR HIGH DEMULTIPLICATIONS.

Description

Friction transmission mechanism.

  The present invention relates to a transmission mechanism

  friction. Preferably, a transmission mechanism is used.

  friction drive for an average gear ratio, when too high requirements are not set in terms of performance and service life. In the most known embodiments, the cylindrical rollers are supported against each other, one of them being

  used as a control wheel and the other as a driven wheel.

  Most often, an embodiment is used which automatically increases the pressure force for a growing moment. In addition, planetary transmission mechanisms in the form of friction mechanisms are known. For the reduction of rotation speed, tapered roller mechanisms and other similar embodiments are incorporated. For high gear ratios, friction transmission mechanisms are used which work according to the principle of harmonic drive according to which a

  thin-walled cylinder-shaped cone is shaped ellipti-

  and is pressurized on a thick-walled cylindrical ring which is chamfered conically to the contact surfaces. This form of construction is also adopted to increase frictional contact surfaces

  with conical annular grooves.

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  The disadvantage in all these known embodiments is

  the contact made on the contact surfaces is only

  linear, and as a result, high periodic pressures occur which make high quality steels necessary. On the other hand, high quality steels have a low coefficient of friction, which

  naturally, is detrimental to the performance and

friction gears.

  The object of the present invention is to provide a friction gear, particularly for high gear ratios, in which the driving and driven portions are in surface contact with each other. By this means it is possible to use specific low surface pressures which also make possible the use of materials having high coefficients of friction. This results in a friction transmission mechanism having dimensions

  weak constructive and good performance.

  This goal is achieved with a cash transmission mechanism.

  comprising an input shaft in connection with a cam-shaped rotating body and a bearing support having an outer race and an elastically deformable inner race, which bears against the rotational body and an output shaft who is in contact with

  a hollow inner cylinder concentric with the rolling ring

  the external cylinder and bearing against it, in that the inner cylinder is deformable and in that a

  outer, non-rotating and deformable cylinder is arranged

  centrically to the inner cylinder by being fitted against its outer surface so that, in the cam region of the rotating body, the inner cylinder is under pressure against the

outer cylinder.

  According to another characteristic of the invention, the hollow outer cylinder is disposed in a blind cylinder-shaped housing in which is carried a bearing of the input shaft while the other bearing of this shaft is mounted in a

recess in the secondary shaft.

  Other characteristics will emerge from the description

  detailed below. The mutual pressure between the two hollow cylinders results from the restoring force of the hollow outer cylinder. This force can be determined by a simple equation. In this one the diameters of the two hollow cylinders, their rigidities of

  wall and deformation play a role of adjustment. Rap-

  port of reduction results from the difference of the di-

  of the two hollow cylinders and a wall stiffness factor which determines the non-circular deformation of these two hollow cylinders, on which account it must be taken into account that the outer fiber of the hollow inner cylinder is elongated and the fiber lying at The inside of the hollow outer cylinder is compressed. Therefore, both surfaces are in thrust one and the other during the circulation of the rotating body and there appears in this way a relative rotation between the hollow inner cylinder and the hollow outer cylinder fixed to the rotation. The direction of rotation is therefore function of the ratio

  rigidity of the walls while the ratio of

  tion is a function of the stiffness ratio of the walls and the

  degree of deformation. We must be careful that the cylinders

  Thin-walled deuces are moved in a non-round circulating deformation relative to one another. By progressive modification of the deformation,

  an adjustable transmission mechanism can be

  gressively for high multiplication ratios. The progressive modification of the deformation can be obtained easily by the fact that devices are provided which gradually adjust with respect to each other the

rotating body cams.

  It is also possible to obtain surface pressurization if one of the two hollow cylinders is made with greater wall urin- gure so that it maintains its round shape longer so that the thin-walled hollow cylinder is at the same time. inside or outside is deformed in such a way that the deformation radii coincide with the midpoint of the rigid hollow cylinder. The stiffness factor of the walls will then be substantially zero.

  the gearing can be obtained in a simple way.

  The invention will be described in more detail below with reference to the accompanying diagrammatic drawings in which:

  Figure 1 is a vertical sectional view of the

  positive friction transmission according to

  the invention; FIG. 2 is a cross-sectional view of

  tical by II-II of Figure 1; FIG. 3 is a representation corresponding to FIG. 2 in which, for the sake of clarity, only the two hollow cylinders are shown in the deformed state;

  Figures 4 and 5 are vertical sectional views

  through the two hollow cylinders in the undeformed and deformed state; Fig. 6 is a reduced scale vertical sectional view of a somewhat modified embodiment of the inner hollow cylinder in the undeformed state; FIG. 7 is a partial view of the arrangement according to FIG. 6 in which the hollow internal cylinder is shown in the deformed state and FIGS. 8 and 9 are partial sectional views of modified embodiments of the hollow internal cylinder of FIG. friction-compliant transmission mechanism

to the invention.

  In Figure 1, the reference 1 designates the driving shaft, the reference 2 refers against the output shaft of the friction transmission mechanism. The output shaft 2 is furthermore connected with a cam-shaped rotating body 3, which in the illustrated embodiment is constituted by two radially adjustable cam members 4, 5 with respect to the cam. and other spacing support relative to each other. In the embodiment shown, the adjustment mechanism is constituted by a threaded spindle mechanism with two threaded spindles 6, 7, one of which has a thread on the left and the other a thread on the right. The two threaded pins 6, 7 are screwed by one of their ends into a thick part of the shaft

  1. At their other end, the two spindles

  6, 7 bear against the parts 4, 5 of the rotary body 3. By an equivalent rotation of the two threaded spindles 6, 7, the two parts 4, 5 of the rotary body 3 are separated one by one.

  on the other, respectively are close to each other.

  It is clear that, for this purpose, another mechanism could be used, for example an automatic adjustment mechanism which

  could be settled not only at standstill but also

  the running of the rotating body 3 'and, hence, the

me of friction transmission.

  As is evident from FIG. 2, each part 4, 5 has as a peripheral trace a segment of a circle while the center of each segment is on a perpendicular axis

  to the longitudinal axis of the driving shaft 1.

  It is further provided a bearing support comprising an elastically deformable inner race 8 and an elastically deformable outer race 9 between

  which are arranged the rolling bodies 10. As the

  1 and 2 of the drawings make it obvious, the elastically deformable inner bearing ring 8 bears against

  the two parts 4 and 5 of the rotary body 3.

  Concentrically to the outer ring 9 of the rolling bearing: 11 is provided a hollow inner cylinder 11 adjacent thereto which is elastically deformable by an appropriate choice of

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  its material, respectively by its configuration. concentrically

  this hollow internal cylinder 11 is arranged with a cylinder

  hollow, deformable, non-rotating hollow outer body resting against the outer surface of the inner cylinder such that in the region of the cams of the rotary body 3 the hollow inner cylinder 11 is pressed against the cylinder

external hollow 12.

  The hollow outer cylinder 12 is, in the form of

  1, disposed in a pot-shaped housing, i.e. a blind cylinder, in which there is provided a bearing 14 of the input shaft while the other bearing 15 of the it is mounted in a recess 16 of

the output shaft.

  As shown in Figure 1 of the drawings, to increase the deformability, recesses are provided in the cylinder

internal hollow 11-.

  FIG. 2 of the drawings makes it obvious to produce large contact surfaces between the two hollow cylinders 11 and 12 over the extent of the angle θ '. As a result, the surface pressure is, relative to the linear pressure, reduced to

a minimum.

  Figure 3 shows in a simpler form a section through the two hollow cylinders 11 and 12 in their deformed form. Reference 18 designates the envelope circle

  allows to appreciate the deformation. For a better representation

  the rotating body 3 has not been shown. Note that the hollow inner cylinder 11 which has, in the unstretched state, that is to say not deformed, a diameter smaller than the hollow outer cylinder 12, has, in the extents of angle t to l state deformed by the rotary body 3 in the form of a cam, a radius of curvature r common with that of the cylinder 11 whose

  centers m are separated by the distance x on both sides of the central

  tral m. In the extent of the angle 90-q / 2 the outer surface of the hollow inner cylinder 11 is detached from the inner surface of the cylinder

external hollow 12.

  FIGS. 4 and 5 explain the kinematic system according to which the two thin-walled cylinders 11, 12 forced into each other mutually repel each other during a rotating non-circular deformation. Around the center

  m, the hollow inner cylinder 11 and the outer cylinder

  12 are engaged by force in one another, whereby the external diameter d2 of the hollow inner cylinder 11 is substantially equal to the internal diameter of the outer cylinder

hollow 12.

  FIG. 5 represents the deformation obtained with the rotary body 3 provided with cams that are not shown when the centers M of the parts 4, 5 of the rotary body 3 are offset by the distance y from the center m. The two hollow cylinders 11, 12 have wall thicknesses s2 and si. Neutral fibers are shown in phantom. Likewise, the common radius R is represented by a dashed dash. It can be seen that the outer fiber of the hollow inner cylinder 11 and the inner fiber of the hollow outer cylinder 12 are elongated by the value AU2 and the inner fiber of the hollow outer cylinder 12 is compressed by the value AU1. During the rotation of the rotary body 3, the two fibers repel each other by the value AU LU2. The two hollow cylinders, which are strongly pressed into each other, are thus, during the rotation of the rotary body 3 provided with cams.

driven in rotation.

  With the embodiment according to FIG. 6, the recesses

  17 are in the form of slots disposed at the periphery of the hollow inner cylinder 11 and offset relative to each other.

  to others in the axial direction.

  FIG. 7 shows that the deformation of the hollow inner cylinder 11 decreases in degrees parallel to each other.

  others with respect to the output shaft 2.

  In the embodiment according to Figure 8 of the drawings, the wall of the hollow inner cylinder is constituted by a plurality of cylindrical portions which are forced into each other. It is advantageous to split each of the cylindrical portions so that these

  parts consist of separate materials.

  The difference between the hollow inner cylinder 11 of FIG. 9 and those of the above embodiments is that the recesses 17 are in the form of longitudinal slots, which ensures easy deformation.

Claims (7)

claims   1. A friction transmission mechanism with a driving shaft connected to a cam-shaped rotating body and a rolling bearing with an elastically deformable outer race and an inner race bearing which abut against the rotary body and with an output shaft which is in connection with a hollow internal cylinder disposed   concentrically to the outer race and against it,   characterized in that the inner cylinder (11) is deformed ble and   in that, concentrically with it, there is arranged a cylinder   hollow outer body (12), deformable and non-rotating resting   against the outer surface of the inner cylinder of such   that the inner cylinder (11) is squeezed into the forming area. cam of the rotating body (3) against the outer cylinder (12). 2. A mechanism according to claim 1, characterized in that the hollow outer cylinder is mounted in a housing (13) in the form of a blind cylinder in which   one of the bearings (14) of the input shaft (1) is mounted.   3. A mechanism according to claim 1, -   characterized in that the further bearing (15) of the input shaft (1) is disposed in a recess (16) in the output shaft (2).   4. A mechanism according to any of the claims i   at 3, characterized in that, to increase the deformability, recesses (17) are provided in the hollow inner cylinder (11), A mechanism according to claim 4, characterized in that the recesses (17) are in the form of 2 4 7 1 5 2 2 longitudinal slots.   6. A mechanism according to claim 4, characterized in that the recesses (17) are formed by slots arranged at the periphery of the hollow inner cylinder (11) and offset relative to one another according to the invention. the axial direction.   7. A mechanism according to any one of the claims 1 to 6,   characterized in that the rotary body (3) is constituted by two parts adjustable in position relative to one another in the radial direction and in support tending to the   away from each other, these parts forming the cams, each   any of these having as profile the shape of a segment circle.   8. A mechanism according to any one of the claims 1-7,   characterized in that the hollow inner cylinder (11) is formed of a plurality of engaged cylinder-shaped parts one in the other.   9. A mechanism according to claim 8, characterized in that each cylindrical portion is split and in that this portion is made from different materials.