EP0961888A1

EP0961888A1 - Mechanical torque converter

Info

Publication number: EP0961888A1
Application number: EP98900932A
Authority: EP
Inventors: Arnold Derek Child
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-01-27
Filing date: 1998-01-21
Publication date: 1999-12-08
Also published as: WO1998032992A1; GB2321505A; GB9701613D0; GB2321505B

Abstract

A torque converter wherein a stationary reactive component is not required, the reactive force being restrained by a force acting on the shorter arm of a lever (33) arranged to pivot about an axis adjacent to the input/output axis (a) on a separate pivot support (29) within the rotatable housing (5). Force is transmitted from the rotatable housing (5) to the longer arm of the lever (33) and the rotational speed of the rotatable housing (5) is dependent on the relative values of input torque and output load. Variation of the rotational speed of the rotatable housing (5) relative to input shaft (14) rotational speed changes the input/output speed ratio, and an infinite variation of the input/output speed ratio is possible within predetermined limits.

Description

MECHANICAL TORQUE CONVERTER

This invention relates to mechanical torque converters and more especially to a stepless variable ratio mechanical torque converter in which the input to output speed ratio and therefore torque multiplication is infinitely variable within predetermined limits. Conventionally continuously variable ratio mechanical transmission systems rely on the pressure acting between untoothed rotating components to transmit torque and on variation of the radial distance at which the pressure acts on rotating components to vary the input to output speed ratio. A control system is required to adjust the relative position of the rotating components.

Torque converters in accordance with this invention are load sensitive and the input to output speed ratio adjusts automatically in response to variation of the relative values of input torque and output load. No control system is necessary and torque is transmitted only via toothed gearing.

The proposed torque converter consists of a torque multiplying gear assembly and a torque splitting gear assembly which transmits part of the multiplied torque to the output shaft and returns the remainder of the multiplied torque to the rotatable housing of the torque multiplying gear assembly. Contained within the rotatable housing are components arranged to modify the effect of reactive force which occurs during torque multiplication and thereby prevent reverse rotation of the rotatable housing which would normally occur in this arrangement. According to the present invention there is provided a torque converter comprising a fixed structure which supports within coaxial bearings an output shaft and the carrier shafts of a rotatable housing in turn supporting within coaxial bearings carrier shafts of an input gearwheel and an annular gearwheel the axes of rotation being coincident with the axis of rotation of the rotatable housing. One carrier shaft of the rotatable housing forms the carrier shaft of a first bevel gearwheel and the output shaft forms the carrier shaft of a second bevel gearwheel.

Intermediate bevel gearwheels are adapted to mesh with the first and second bevel gearwheels to form a differential unit and the carrier shafts of the intermediate bevel gearwheels form a cross member integral with the carrier shaft of the annular gearwheel with axis of rotation coincident with the axis of rotation of the rotatable housing. An intermediate shaft with axis of rotation not coincident with the axis rotation of the rotatable housing is the carrier shaft of an annular gearwheel adapted to mesh with the input gearwheel. The said intermediate shaft is also the carrier shaft of a gearwheel adapted to mesh with the annular gearwheel with axis of rotation coincident with the axis of rotation of the rotatable housing. A projection within the rotatable housing is arranged to contact a roller bearing in turn contacting the longer arm of a lever with pivot not coincident with the axes of rotation of the rotatable housing or intermediate shaft. The pivot of the lever is preferably the axis of rotation of a system consisting of a convex face or faces which are an integral part of the lever and are supported on roller bearings held within a concave track or tracks of a pivot support positioned on roller bearings within the rotatable housing and with an axis of rotation coincident with the axis of rotation of the rotatable housing. The intermediate shaft is located within the bearing surface of a shaft support which contacts the shorter arm of the said lever along two or more individual lines or continuously between two individual lines preferably parallel to the rotational axis of the intermediate shaft. A ball bearing or bearings are located between the shaft support and the rotatable housing and a roller bearing or bearings are located between the shaft support and the pivot support. The shaft support and the shorter arm of the lever incorporate guides to maintain the relative positions of these components longitudinally and transversely. The pivot support and the rotatable housing incorporate guides to maintain the relative positions of these components longitudinally. The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which:

FIGURE 1 is a side view depicting the disposition of the gearwheels and carrier shafts of the torque multiplying and torque splitting gear assemblies of the proposed torque converter.

FIGURE 2 is a cross view of figure 1 depicting the supporting components within the rotatable housing of the torque multiplying gear assembly.

FIGURE 3 is a cross view of two sections of figure 1 each section depicting the relative positions of a gearwheel meshed with the complimentary teeth of an annular gearwheel.

FIGURE 4 is an isometric view in simplified form of the assemblies depicted in figure 1 and includes linear representation of torque values.

FIGURE 5 is an analysis of the forces acting throughout the torque converter during the two extreme operating conditions.

FIGURE 6 is an isometric view in simplified form of two coupled torque multiplying gear assemblies similar to that depicted in figure 1 forming a single unit connected to a torque splitting gear assembly similar to that depicted in figure 1.

FIGURE 7 is an analysis of the performance throughout the operating range of a dual unit as depicted in figure 6 and including two sets of components similar to that depicted in figure 2. Reference will firstly be made to figure 1 of the drawings. The carrier shafts 6 and 7 of rotatable housing 5 are supported within coaxial bearings 2 and 3 of fixed structure 1. The rotatable housing 5 supports within bearing 11 which is coaxial with bearing 2 input shaft 14 which is the carrier shaft of gearwheel 15. The rotatable housing 5 also supports within bearing 12 which is coaxial with bearing 3 shaft 20 which is the carrier shaft of annular gearwheel 19. Carrier shaft 7 of rotatable housing 5 forms the carrier shaft of bevel gearwheel 8 and fixed structure 1 supports within bearing 4 which is coaxial with bearing 3 output shaft 10 which is the carrier shaft of bevel gearwheel 9 which has the same number of teeth as bevel gearwheel 8. Shaft 20 is supported by a second bearing 13 within output shaft 10. The teeth of bevel gearwheels 8 and 9 mesh with complimentary teeth of bevel gearwheels 25 and 26 which are supported by bearings 23 and 24 of carrier shafts 21 and 22 which form an integral cross member of shaft 20. Shaft 17 which is not coaxial with the other shafts is the carrier shaft of annular gearwheel 16 and gearwheel 18.

Reference will now be made to figure 2 of the drawings. A projection on the inside of rotatable housing 5 contacts a roller bearing 34 which in turn contacts the longer arm of a lever 33 which is supported by convex projections 32 formed each side of lever 33. The projections 32 are supported via roller bearings resting on the concave tracks.31 of pivot support 29 which is supported via roller bearings on an inner surface of rotatable housing 5. Shaft support 28 which supports shaft 17 within bearing 27 includes lobes which contact the shorter arm of lever 33 at two points. A ball bearing 35 preferably located by uncompressed springs is positioned between shaft support 28 and rotatable housing 5 and a roller bearing 30 located by uncompressed springs is positioned between shaft support 28 and pivot support 29. A pilot pin 36 is positioned between the shaft support 28 and the shorter arm of lever 33 and a guide 37 is positioned between the pivot support 29 and rotatable housing 5. Preferably a spring 38 under compression is positioned between shaft support 28 and rotatable housing 5. The roller bearings supporting pivot support 29 and lever projections 32 would include means (not shown) to maintain the relative position of the roller bearings. Reference will now be made to figure 3 of the drawings. In one embodiment of the gearwheel assemblies depicted in figure 1 gearwheel 15 and annular gearwheel 16 have respectively 16 and 32 teeth and gearwheel 18 and annular gearwheel 19 have respectively 32 and 48 teeth.

For the purpose of analysis to be conducted with the aid of figure 4 and figure 5 forces will be considered to act between the meshing gearwheel teeth at the radial distance of the pitch circle in the direction of a tangent to the pitch circle. Gearwheel 15 and annular gearwheel 16 have pitch circle radii respectively 16mm and 32mm and gearwheel 18 and annular gearwheel 19 have pitch circle radii respectively 32mm and 48mm. Forces acting on shafts are considered to act via the rotational axes of the shafts.

Reference will now be made to figure 4 of the drawings. For the purpose of the following analysis it is to be assumed that shaft 17 is free to rotate within a bearing supported by rotatable housing 5. If output shaft 10 and rotatable housing 5 are held stationary and a torque F16 (force F acting at 16mm from axis a) applied to input shaft 14 the torque values depicted will be generated. A force F will act between the teeth of gearwheel 15 and annular gearwheel at 16mm from axis a and a reactive force F will act in a parallel direction via the rotational axis c of annular gearwheel 16 at 16mm from axis a. The force F acting on annular gearwheel 16 about axis c will generate a torque F32 (force F acting at 32mm from axis c) in shaft 17 which will be transmitted to gearwheel 18. The force F acting between the teeth of gearwheel 18 and annular gearwheel 19 at 32mm from the rotational axis c of gearwheel 18 will generate a reactive force F in a parallel but opposite direction via axis c at 16mm from axis a and a torque F48 (force F acting at 48mm from axis a) in annular gearwheel 19. Torque transmitted from annular gearwheel 19 via carrier shaft 21 to bevel gearwheel 25 will be split equally by the differential unit, F24 units torque via bevel gearwheel 9 to output shaft 10 and F24 units torque via bevel gearwheel 8 to rotatable housing 5. The torque F32 (force 2F acting on shaft 17 via axis c at 16mm from axis a) is greater than that torque F24 returned to rotatable housing 5 which if released would rotate in a reverse direction to input shaft 14 which would commence to rotate simultaneously. Reference will now be made to figure 5 (A) of the drawings. In accordance with the previous analysis a load is applied to the output shaft and a torque F16 applied to the input shaft but in this analysis the rotatable housing 5 is free to rotate. Reverse rotation of the unrestrained rotatable housing 5 can be prevented if shaft support 28 of shaft 17 is arranged to contact the shorter arm of lever 33 via two lobes at 24mm and 12mm from axis b. The reactive force 2F acting on shaft support 28 via axis c is constrained by roller bearing 30 to act on the shorter arm of lever 33 in the direction of a chord of the circle described by axis a as centre. The force 0.5F (the force element of F24 units torque) acting on rotatable housing 5 at 48mm from axis a and transmitted via roller bearing 34 to act on the longer arm of lever 33 at 72mm from axis b will generate a torque F36 which will act on the lever 33 about axis b.

The reactive force 2F acting via axis c will initially act via the first lobe of shaft support 28 which is 24mm from axis b but movement of the shorter arm of lever 33 about axis b cannot occur because parallel movement of the second lobe would separate the first lobe from its contact point. This constraint will cause the reactive force 2F acting via axis c to be divided equally between the two lobes of shaft support 28 to act on the shorter arm of lever 33 about axis b and the two component torques generated, F12 (force F acting at 12mm from axis b) and F 24 (force F acting at 24mm from axis b) produce a total torque F36 about axis b which is equal to the opposing torque generated via the longer arm of lever 33. Axis c is located 24mm from the contact point of the first lobe of shaft support 28 and the force F which via lever 33 opposes the force F acting via the second lobe of shaft support 28 which is 12mm from the first lobe will generate a torque F12 about the first lobe and a resultant force 0.5F which will act on shaft support 28 via axis c in the direction of a radius of the circle described by axis a as centre.

Because equal but opposite forces oppose the forces generated in the lobes of shaft support 28 equilibrium is established and movement of shaft support 28 is prevented and in consequence all associated components including rotatable housing 5 will remain stationary, if insufficient torque is generated to overcome the load acting on the output shaft 10. Reverse rotation of rotatable housing 5 cannot occur and if only F24 units torque are required to overcome the load acting on the output shaft 10 the rotatable housing 5 and its bevel gearwheel 8 will remain stationary while relative rotation of the remaining gearwheels will commence and the output shaft will rotate. The load acting on the transmission will resist relative rotation of the gearwheels and cause the force F acting between gearwheel 15 and annular gearwheel 16 to attempt to rotate the whole mechanism as a unit and if the load acting on output shaft 10 is reduced the F16 units torque (force F acting 16mm from axis a) plus the torque F24 acting on rotatable housing 5 about axis a will produce a total of F40 units of torque which is sufficient to overcome the reactive force 2F acting 16mm from axis a and rotation of rotatable housing 5 will commence, reducing relative rotation of the gearwheels and thereby reducing the input to output speed ratio and torque multiplication through the system. Further reduction of the load on output shaft 10 will result in increased rotation of rotatable housing 5 and if the load on output shaft 10 is reduced to a level at which only F16 units input torque is required to overcome the load acting on the output shaft 10 rotatable housing 5 will reach input shaft rotational speed and the whole mechanism will rotate as a unit to give direct drive at which stage the forces then acting on the mechanism will be as depicted in figure 5 (B).

When the pivot (axis b) of lever 33 is stationary the total force transmitted from rotatable housing 5 to the longer arm of lever 33 will act about the pivot (axis b) but when the rotatable housing 5 and therefore the pivot (axis b) commence to rotate about axis a this condition will change.

Increase in the rotational speed of the pivot (axis b) about axis a will produce a corresponding reduction in the value of the torque acting on the longer arm of lever 33 about the pivot (axis b) and a simultaneous increase in the effect of the torque acting on rotatable housing 5 about axis a and thereby acting on lever 33 and shaft support 28 about axis a. Simultaneous reduction in the relative rotation of the gearwheels will occur and thereby reduce the reactive force acting via axis c and the corresponding forces acting on the shorter arm of lever 33. When rotatable housing 5 attains the rotational speed of the input shaft the longer arm of lever 33 will have the same rotational speed about axis a as the pivot (axis b) and will produce no further torque effect about the pivot (axis b). The torque acting on the rotatable housing 5 about axis a will now act on lever 33 and shaft support 28 and rotate these components as a unit about axis a. Relative rotation of the gearwheels will cease and in consequence no reactive force will act via axis c and no corresponding forces will act on the shorter arm of lever 33 about the pivot (axis b). The torque transmitted via annular gearwheel 19 to the intermediate bevel gearwheels of the differential unit is now the sum of the input torque plus torque recycled via the rotatable housing 5 which has the same value as input torque.

The reactive forces acting via axis b produce no resultant reverse torque about axis a and for the purpose of the analysis can be ignored and are reduced to zero when the rotatable housing 5 attains input shaft rotational speed.

An increase in the transmission load during direct drive will reverse the sequence explained above and increase torque multiplication. Also the rotational speed of the rotatable housing will be directly influenced by any variation in the magnitude of the input torque. Thus the mechanism will respond to any change in the relative values of the input torque and the transmission load continuously to produce optimum torque output.

Reference will now be made to figure 6 of the drawings. To provide an increased ratio range for automotive or other applications two or more torque multiplying gear assemblies can be connected in series, the output shaft of one assembly forming the input shaft of the next assembly as depicted with a common rotatable housing enclosing the torque multiplying gear assemblies.

Reference will now be made to figure 7 of the drawings. The graph depicts the relationship between output torque output rpm and rotatable housing rpm when constant input torque applied at constant rpm. It is to be understood that the foregoing is merely exemplary of one embodiment of a torque converter in accordance with the invention and that modification can readily be made thereto without departing from the true scope of the invention as set out in the appended claims.

For the successful operation of the mechanism as described it is essential that transfer of the total force acting on the rotatable housing should occur between the rotatable housing and the longer arm of the lever and the extensive use of ball or roller bearings in the design will for practical purposes eliminate frictional forces which would disturb the balance of forces described. It may however be possible to utilise other types of bearing which would give acceptable frictional losses.

It is to be assumed that if helical gearwheels are utilised in the torque multiplying gear assembly axial thrust on the intermediate shaft can be substantially reduced if the gearwheels are suitably designed to balance the axial forces acting on the shaft.

The preferred embodiment of the invention as described would utilise a bevel gearwheel differential to give an equal torque split but an alternative embodiment could utilise a bevel gearwheel differential to give an unequal torque split. In a further embodiment of the invention the bevel gearwheel differential could be replaced by an alternative differential gearwheel arrangement.

Claims

1. A torque converter comprising an input gearwheel arranged to mesh with an annular gearwheel, the carrier shaft of the said annular gearwheel also forming the carrier shaft of a gearwheel arranged to mesh with an intermediate annular gearwheel, the carrier shaft of the said intermediate annular gearwheel including projections which provide bearing surfaces to support gearwheels arranged to mesh with both an output gearwheel and a gearwheel supported by a carrier shaft forming an integral extension of a rotatable housing.

2. A torque converter as claimed in Claim 1 wherein the carrier shaft of the said annular gearwheel arranged to mesh with the said input gearwheel is supported by the bearing surface of a shaft support, the said shaft support in turn supported by the shorter arm of a lever arranged to pivot on a separate pivot support located within the said rotatable housing and the longer arm of the said lever arranged to contact a bearing, the said bearing in turn arranged to contact a projection within the said rotatable housing.

3. A torque converter as claimed in Claim 1 or Claim 2 wherein the said shaft support is arranged to contact the shorter arm of the said lever by means of protrusions forming an integral part of the said shaft support.

4. A torque converter as claimed in Claim 1 o╧ä Claim 2 wherein the said shaft support is arranged to contact an area of the shorter arm of the said lever.

5. A torque converter as claimed in any one of Claims 1 to 4 wherein the said pivot support is in turn supported by bearings located on the inner surface of the said rotatable housing.

6. A torque converter as claimed in any one of Claims 1 to 5 wherein the relative positions of the components within the said rotatable housing are maintained by fixed guides, bearings which service as guides and springs.

7. A plurality of torque converters as claimed in any one of the preceding claims wherein the carrier shaft of the said intermediate annular gearwheel forms the input shaft of a following unit.