WO1997033106A1 - Mecanisme differentiel - Google Patents

Mecanisme differentiel Download PDF

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Publication number
WO1997033106A1
WO1997033106A1 PCT/GB1997/000605 GB9700605W WO9733106A1 WO 1997033106 A1 WO1997033106 A1 WO 1997033106A1 GB 9700605 W GB9700605 W GB 9700605W WO 9733106 A1 WO9733106 A1 WO 9733106A1
Authority
WO
WIPO (PCT)
Prior art keywords
output
cam
output cam
friction
followers
Prior art date
Application number
PCT/GB1997/000605
Other languages
English (en)
Inventor
Alastair John Young
John Philip Chippendale
Original Assignee
Automotive Products Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Automotive Products Plc filed Critical Automotive Products Plc
Priority to GB9721910A priority Critical patent/GB2314595B/en
Priority to JP9531571A priority patent/JPH11504698A/ja
Priority to EP97905336A priority patent/EP0824642A1/fr
Publication of WO1997033106A1 publication Critical patent/WO1997033106A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H48/00—Differential gearings
    • F16H48/12—Differential gearings without gears having orbital motion
    • F16H48/14—Differential gearings without gears having orbital motion with cams
    • F16H48/147—Differential gearings without gears having orbital motion with cams with driven cam followers or balls engaging two opposite cams

Definitions

  • the invention relates to a differential mechanism particularly but not exclusively for use in motor vehicles.
  • Differential mechanisms commonly used on vehicles are of the sun and planet gear type and have a well known disadvantage that when one wheel is on a slippery surface such as mud or ice and the other wheel is on a firm surface capable of providing traction, the first wheel will simply spin as it receives all the available power transmitted to the differential.
  • a differential mechanism comprising two output cam members rotatable about an axis, each said member having a single frustoconical cam surface thereon of undulating form comprising pairs of mutually inclined surfaces, a plurality of cam followers having end surfaces engaging the cam surfaces of the output cam members, the arrangement being such that relative rotation of said output cam members causes the cam followers to slide axially, an input member which slidably supports the followers and moves the followers circumferentially relative to the output cam members, a first friction surface operatively associated with at least one output cam member and inclined at an acute angle to a plane normal to the axis of rotation of the output cam members, and a second similarly inclined friction surface operatively associated with the input member or the other output cam member, the first and second friction surfaces frictionaily engaging each other and generating a frictional torque which modifies the ratio of the torque
  • Each output cam member may be provided with an inclined first friction surface which engages a respective inclined second friction surface on the input member or the other output cam member.
  • the first and second friction surfaces may be detachably secured to the associated output cam member and input member respectively to enable easy adjustment of the angle of inclination of the surfaces to vary the performance of the mechanism.
  • the first and second friction surfaces are preferably formed on co-operating friction rings which are secured to the associated output cam member and input member or other output cam member.
  • the first and/or second friction surfaces may be splined to the associated output cam member and/or input member or other output cam member.
  • the first and/or second friction surfaces may be pinned or pegged to the associated output cam member and/or input or other output cam member via integral or separate pins or pegs.
  • the invention also provides a method of providing a differential whose output torque ratio can be varied, said method comprising;-
  • a differential mechanism comprising two output cam members rotatable about an axis, each said member having a single frustoconical cam surface thereon of undulating form comprising pairs of mutually inclined surfaces, a plurality of cam followers having end surfaces engaging the cam surfaces of the output cam members the arrangement being such that relative contra rotation of said output cam members causes the cam followers to slide axially, and an input member which slidably supports the followers and moves the followers circumferentially relative to the output cam members;
  • Figure 1 is a cross-section through a differential mechanism in accordance with the invention taken through output cam members;
  • Figure 2 is an end view of the differential of Figure 1 shown partly broken away;
  • Figures 3a - 3d are developments of symmetrical cam surfaces with cam followers shown in positions therebetween at different relative displacements along the cam surfaces;
  • Figure 4 is a diagrammatic end view of a follower
  • Figure 5 is a section on line V-V of Figure l;
  • Figure 6 is an exploded perspective view of the differential of Figure 1;
  • Figure 7 shows the forces acting on friction rings located between the output cam members and an input member of the differential mechanism of Figure 1;
  • Figure 8 shows the forces applied to the output cam members by the cam followers during differential action which give rise to the inherent torque output bias of the differential mechanism
  • Figure 9a to 9e show a range of different co-operating friction rings which generate different friction torques
  • Figure 10 shows scrolling grooves on a friction ring to promote better lubrication
  • FIGS 11,12 & 13 show details of alternative friction ring constructions
  • Figure 14 shows an inter axle differential mechanism embodying the present invention.
  • the differential 10 is mounted in a partially oil filled surrounding casing (not shown) by bearings (also not shown).
  • the differential 10 comprises a housing 11 having a gear 12 on its external surface which receives drive from a pinion (not shown) in known manner.
  • the gear 12 is drivably connected to end walls 13, 14 which may be formed integrally of the housing 11 or maybe formed separately and held in the housing 11 by any suitable means such as by bolts 11a.
  • Two output cam members 16, 17 have splines 15 at the centre thereof to drive output shafts (not shown) extending through bores 18 in the end walls 13, 14.
  • the bores 18 may each have a helical oil feed groove (not shown) on the inner surface thereof in use to feed lubrication into or out of the differential.
  • the output cam members 16, 17 may be supported for rotation about an axis X within end walls 13 and 14 in bearings (not shown). Alternatively, as shown, no such bearings may be used since the design does not produce any significant radial misalignment forces on members 16 and 17.
  • the output cam members 16, 17 each have a respective undulating cam surface 22, 23 thereon which comprises a frustoconical undulating surface.
  • the cam surface 22 comprises an annular zigzag surface shown in detail in Figure 3 made up from a number of pairs of mutually inclined helical surfaces 24, 25.
  • the cam surface 23 also comprises an annular zigzag surface which, as is apparent from Figure 3, has the same number of pairs of mutually inclined helical surfaces 26, 27 as used on surface 22.
  • the undulating cam surfaces 22 and 23 are inclined at an angle P to the axis x-x whereby each cam surface converges radially inwardly towards the other.
  • Cam followers 28 are positioned between the cam surfaces 22, 23.
  • Each cam follower is of strut-like elongate form and comprises two sets of mutually inclined end surfaces 29, 30, 32 and 33 which terminate at the side surfaces 34,35 (See Figure 3).
  • the angle of inclination Q (see Figure 3C) between the end surfaces 29, 30 corresponds to the angle of inclination between the mutually inclined surfaces 24, 25.
  • each cam follower is arcuate which enables the followers to be assembled together in an annular array as viewed in Figure 2.
  • Each cam follower has an arcuate embrace of substantially 360/nf degrees where nf is the number of cam followers.
  • the arcuate embrace may be less to leave clearance spaces 28' (see Figure 4) between the followers thus preventing drive by abutment between adjacent followers.
  • Each cam follower includes an elongate drive dog 36 having mutually inclined side surfaces 37, 38 ( Figure 4).
  • the drive dogs 36 locate with slight clearance 36a in complementary shaped grooves 39 formed in the inner periphery of a cylindrical drive input element 40 formed on input housing 11.
  • the clearance 36a is just sufficient to ensure that the arcuate outer periphery (indicated at 28a) of each follower 28 can abut the inner peripheral surface (40a) of the drive input element 40.
  • the grooves 39 provide support for the followers 28 at least adjacent their axial ends and preferably, as shown, for substantially their entire length.
  • the assembly of the cam followers 28 is preferably such as to place the side surfaces 34, 35 of adjacent followers so that they interengage or lie closely adjacent. In that way maximum use is made of the available circumferential space for the cam followers, the followers together forming a substantially continuous and compact annular array as viewed in Figure 2.
  • cam surfaces 22, 23 are identical having symmetrical pairs of inclined surfaces 24, 25 and 26, 27 respectively which are both inclined relative to each other at angle Q.
  • the drive surfaces 24, 26 are a circumferential length LI which is equal to the circumferential length L2 of the overrun surfaces 25, 27.
  • cam followers 28 In order that the cam followers 28 cannot shuffle through the gap between an opposed peak and an opposed trough on the undulating cam surfaces 22, 23 without providing drive, it is necessary for different cam followers to be provided.
  • cam followers are arranged such that the number of followers is a multiple of a single wave length.
  • the number of followers is a multiple of a single wave length.
  • there are two cam followers per wave length one wave length being the distance spanned by each pair of mutually inclined surfaces 24, 25 and 26, 27).
  • cam followers 28 are provided in groups of four followers 28A, 28B, 28C, 28D.
  • the followers 28 have peaks which are offset from a reference line, in this case the centre line of each follower.
  • followers 28A and 28D are identical and the followers 28B and 28C are identical, the follower 28B being a mirror image (in plan view only) of the adjacent follower 28A and the follower 28C being a mirror image of the adjacent follower 28D.
  • followers 28A' and 28B' are in the next group. There are therefore two types of follower and to assist recognition of the different types, one type of follower has its drive dogs 36 grooved at 36a (See Figures 5 and 6) . In Figure 3a the followers 28A and 28C provide drive, whilst the followers 28B and 28D take the load in reverse.
  • cam followers When drive input is applied through drive input housing 11, and assuming that a vehicle having the differential is being driven in a straight line, the cam followers apply a load to cam surfaces 22, 23 so as to rotate the output cam members 16, 17 at equal speeds.
  • the cam follower 28A on the extreme left has its end surfaces 29, 32 in driving engagement with surfaces 24, 26 and alternate followers are similarly in driving engagement with the cam surfaces 22, 23.
  • intermediate cam followers have their surfaces in non-driving engagement with the cam surfaces as discussed above.
  • the driving force applied by the followers 28 to the inclined surfaces 24, 26 produces a reaction force F as illustrated in Figure 4.
  • the inclination of the end surfaces of the cam followers at angle P causes the application of forces, which are shown only for cam 22 having the angle P.
  • the application of force F creates an outward force G thereby producing a resultant force R which passes radially outboard of edge E preferably approximately through or adjacent a corner Cl between the drive dog 36 and an adjacent outer peripheral part of the follower 28. In that way the loading on the cam follower tends to wedge it firmly against a corner C2 of the drive input element 40 in such a way that tipping of the follower about its edge E is avoided.
  • cam surfaces 22, 23 causes the cam followers 28 to move axially and it can be seen in 3c that the followers 28B and 28C are sitting on a cam peak on cam surfaces 23 and 22 respectively and provide no drive.
  • the follower 28A is providing drive whilst the follower 28D is available to take overrun or reverse loading.
  • the length (and hence area) of the follower drive faces 29 and 32 (which engage the inclined surfaces 24 and 26 respectively) are in a ratio a/b and c/d in relation to the length of the overrun follower faces 29 and 33, which engage the inclined cam surfaces 25 and 27 respectively.
  • cam followers for two cam waves and for a balanced design from two upto ten cam waves.
  • Friction rings 16a and 17a each have first friction surfaces 16c and 17c respectively which are inclined to a plane normal to axis X - X at an acute angle W and which contact second friction surfaces 13c and 14c on second friction rings 13a and 14a which are splined to end walls 13 and 14 at 13b and 14b respectively.
  • Axial float of the output cam members 16 and 17 within end walls 13 and 14 is controlled by a shim ring 60 and a belleville washer 61 located between friction ring 14a and end wall 14 and between friction ring 13a and end wall 13 respectively.
  • the normal reaction force N is balanced by an axial thrust component FA and a radial thrust component FR (see Figure 7) applied at the contact area between rings 13a and 16a.
  • the radial component FR of thrust is internally balanced within ring 13a leaving axial component FA to contribute to the friction torque generated between rings 13a and 16a.
  • the torque output bias ratio of the differential can be adjusted as required by a particular vehicle application or particular course on which the vehicle is to be run. For example, on particular tracks with more severe corners it may be advantageous to have a higher torque bias.
  • Figures 9a to 9e show a range of co-operating friction rings 13a, 16a with different angles of inclination W which generate different levels of friction torque FT. Rings 13a and 16a in Figure 9a generate the highest friction torque and the rings 13a and 16a in Figure 9e generate the lowest friction torque.
  • Figure 1 shows lubrication apertures 70 formed in end walls 13 and 14 through which oil contained within the differential casing is forced as the input member 11 and end walls 13, 14 rotate.
  • This oil flows between the contacting friction ring surfaces 13c 16c and 14c, 17c via one or two way scrolling grooves formed in the friction surfaces (see grooves 71 of Figure 10).
  • the friction ring surfaces can be provided with grooves 72 through which the oil can flow to lubricate these surfaces.
  • one of the friction surfaces of each co-operating pair e.g. 13c, 16c or 14c, 17c
  • the oil which enters via apertures 70 fills-up the radially outer portion 73 of the volume encased by input member 11 and end walls 13 and 14.
  • Figure 12 shows an alternative construction in which friction ring 16a is connected with output cam member 16 via cast in pegs 16b.
  • Figure 13 shows a construction in which separate pins 16b engage slots 16d in friction ring 16a rather than simple peg bores.
  • the invention is also applicable to interaxle differentials of the forum described in the Applicants European Patent Application EP-A-0619863, one example of which is shown in Figure 14. with components of a similar function to components shown in Figure 1 multiplied by 10.
  • Input to this differential is via an input hub 160 which is connected via splines 161 to an input shaft 162.
  • Output cam member 170 is connected via splines 171 with output shaft 172 and the other output cam member is formed on end wall 130.
  • Cam followers 280 act between cam surfaces 220 and 230 which face inwards towards the axis of rotation X-X.
  • followers 280 are connected with input hub 160 via drive dogs 360 which engage groove 390 in hub 160.
  • a pair of cooperating frictions rings 170a. 140a act between the outputs of the differential and again increase the torque bias ratio of the differential.
  • a differential with identical output cam members is used in a circuit racing application, it may be that on a particular circuit, there are one or more very tight corners in one direction, while the corners in the opposite direction are mainly of a more sweeping nature. In such cases it may improve the handling of the vehicle, and hence the overall performance, if the torque bias ratio for cornering in one direction is set higher than that for the opposite direction.
  • This effect may also be advantageous in centre differential applications (i.e inter axle differentials) in four wheel drive vehicles.
  • one option is to have a needle thrust bearing at one end and an angled friction ring at the other end.
  • This arrangement can enable an unequal torque bias set-up to be equalised, as well as providing an extension to the options where an unequal performance is desired (lowering the bottom end of the range of possible torque bias ratios) .

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Retarders (AREA)

Abstract

Un mécanisme différentiel comporte deux cames de sorties (16, 17) susceptibles de tourner autour d'un axe X-X, chacune de ces cames de sortie ayant une surface tronconique unique (22, 23) de forme ondulatoire comportant des paires de surfaces inclinées (24, 25:26, 27) les unes par rapport aux autres. Des contre-cames (28) comportent des surfaces terminales (29, 30:32, 33) qui entrent en contact avec les surfaces (22, 23) des cames de sortie de façon à ce que la rotation relative desdites cames de sortie (16, 17) entraîne un glissement axial des contre-cames (28). Un élément d'entrée (11) supporte, de manière coulissante, les contre-cames (28) et les déplace circonférentiellement par rapport aux cames de sortie (22, 23). Une première surface de frottement (16c) est fonctionnellement associée à au moins une des cames de sortie (16, 17) et inclinée suivant un angle aigu W par rapport à un plan perpendiculaire à l'axe de rotation X-X des cames de sortie. Une seconde surface de frottement (13c) inclinée de manière similaire est fonctionnellement associée à l'élément d'entrée (11, 13, 14). Les première et seconde surfaces de frottement (16c, 13c) sont accouplées par contact de frottement et elles génèrent un couple de frottement (FT) qui modifie le rapport de la sortie du couple des cames de sortie (16, 17) lorsque se produit une rotation relative entre les cames de sortie.
PCT/GB1997/000605 1996-03-07 1997-03-06 Mecanisme differentiel WO1997033106A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB9721910A GB2314595B (en) 1996-03-07 1997-03-06 A differential mechanism
JP9531571A JPH11504698A (ja) 1996-03-07 1997-03-06 ディファレンシャル機構
EP97905336A EP0824642A1 (fr) 1996-03-07 1997-03-06 Mecanisme differentiel

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9604844.2 1996-03-07
GBGB9604844.2A GB9604844D0 (en) 1996-03-07 1996-03-07 A differential mechanism

Publications (1)

Publication Number Publication Date
WO1997033106A1 true WO1997033106A1 (fr) 1997-09-12

Family

ID=10790002

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1997/000605 WO1997033106A1 (fr) 1996-03-07 1997-03-06 Mecanisme differentiel

Country Status (5)

Country Link
EP (1) EP0824642A1 (fr)
JP (1) JPH11504698A (fr)
KR (1) KR100560377B1 (fr)
GB (2) GB9604844D0 (fr)
WO (1) WO1997033106A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021983A1 (fr) * 1999-09-18 2001-03-29 Ap Hydraulics Limited Mecanismes de differentiels
US7604562B2 (en) 2005-08-31 2009-10-20 Engineering Center Steyr Gmbh & Co. Kg Drive axle for a light vehicle

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1035491B (de) * 1956-11-02 1958-07-31 Daimler Benz Ag Selbstsperrendes Ausgleichsgetriebe, insbesondere fuer Kraftfahrzeuge
DE1039373B (de) * 1956-09-01 1958-09-18 Daimler Benz Ag Ausgleichgetriebe, insbesondere fuer Kraftfahrzeuge
GB2136894A (en) * 1980-03-04 1984-09-26 Schou Carl Einar Positive clutch differential
WO1988007148A1 (fr) * 1987-03-19 1988-09-22 Bernard, Derek, John, Charles Ameliorations relatives a des mecanismes de differentiels.
US4782720A (en) * 1985-11-12 1988-11-08 Tochigifujisangyo Kabushikigaisha Power transmission unit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2266126A (en) * 1992-04-15 1993-10-20 Automotive Products Plc Camming differential mechanism has frictional engagement between cam output member and input
GB9312856D0 (en) * 1993-06-22 1993-08-04 Automotive Products Plc A differential mechanism

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1039373B (de) * 1956-09-01 1958-09-18 Daimler Benz Ag Ausgleichgetriebe, insbesondere fuer Kraftfahrzeuge
DE1035491B (de) * 1956-11-02 1958-07-31 Daimler Benz Ag Selbstsperrendes Ausgleichsgetriebe, insbesondere fuer Kraftfahrzeuge
GB2136894A (en) * 1980-03-04 1984-09-26 Schou Carl Einar Positive clutch differential
US4782720A (en) * 1985-11-12 1988-11-08 Tochigifujisangyo Kabushikigaisha Power transmission unit
WO1988007148A1 (fr) * 1987-03-19 1988-09-22 Bernard, Derek, John, Charles Ameliorations relatives a des mecanismes de differentiels.

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021983A1 (fr) * 1999-09-18 2001-03-29 Ap Hydraulics Limited Mecanismes de differentiels
GB2358682A (en) * 1999-09-18 2001-08-01 Ap Hydraulics Ltd Differential mechanisms
US7604562B2 (en) 2005-08-31 2009-10-20 Engineering Center Steyr Gmbh & Co. Kg Drive axle for a light vehicle

Also Published As

Publication number Publication date
GB2314595B (en) 2000-07-12
GB2314595A (en) 1998-01-07
GB9604844D0 (en) 1996-05-08
EP0824642A1 (fr) 1998-02-25
KR19990008369A (ko) 1999-01-25
KR100560377B1 (ko) 2007-07-09
GB9721910D0 (en) 1997-12-17
JPH11504698A (ja) 1999-04-27

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