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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
  • B60K17/00—Arrangement or mounting of transmissions in vehicles
  • B60K17/04—Arrangement or mounting of transmissions in vehicles characterised by arrangement, location or kind of gearing
  • B60K17/16—Arrangement or mounting of transmissions in vehicles characterised by arrangement, location or kind of gearing of differential gearing
• • 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
  • F16H48/06—Differential gearings with gears having orbital motion
• • 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
• • 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
  • F16H2048/02—Transfer gears for influencing drive between outputs
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T74/00—Machine element or mechanism
  • Y10T74/19—Gearing
  • Y10T74/19005—Nonplanetary gearing differential type [e.g., gearless differentials]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T74/00—Machine element or mechanism
  • Y10T74/19—Gearing
  • Y10T74/19023—Plural power paths to and/or from gearing
  • Y10T74/19042—Friction-type gearing

Definitions

• the present invention relates to differential drive mechanisms and is concerned with such mechanisms of the type which comprise a cage which is rotatable about an axis and represents the input, two coaxial output shafts which are rotatable with respect to the cage about the said axis, a coupling which is connected eccentrically to the two output shafts to transmit relative contra- rotational movement between them by connections which permit relative rotation of the coupling and the output shafts about an axis substantially parallel to the said axis and a restraint member which is coupled to the cage and to the coupling such that the coupling is rotatable with respect to the cage about an axis substantially perpendicular to the said axis and capable of reciprocating movement in a direction perpendicular to the said axis but prevented from movement in a direction parallel to the said axis, the eccentric connection of the coupling and the output shafts including a respective eccentric hole formed in the inner end of each output shaft in which the associated end of the coupling is received, the ends of the coupling having a part- sp
• the torque bias ratio desirably has value of say 2 to 3 but in the event that one outpu shaft is rotating very much more rapidly than the other, that is to say the differential is differentiating a high speed, it is desirable that the torque bias rati should have as high a value as possible so that th maximum amount of torque is transmitted to the mor slowly rotating output shaft. This is desirable so as t ensure that power is not expended spinning a vehicl wheel and that the maximum amount of power is availabl to the other wheel to drive the vehicle over the patch o mud or the like. It is, therefore, desirable that th torque bias ratio is strongly speed dependent, that is t say increases substantially with increased speed o differentiation.
• Differentials of the type referred to above inherentl have little or no speed sensitivity of the torque bia ratio due to the fact that the frictional torque i substantially independent of speed.
• a speed dependen torque transfer is desirable and it is therefore a object of the present invention to provide a differentia of the type referred to above which has a substantia speed sensitivity of the torque bias ratio.
• a differential driv mechanism of the type referred to above is characterise in that one or more portions of the coupling or of member connected to it constitute a piston which i slidably received in a respective cylinder defined by further component or components of the differential driv 73
• the said portion(s) of the coupling or o the said member or one of the said further component defines a restricted passage which connects the cylinde to a further space, whereby when differential rotation o the output shafts occurs a fluid within the cylinder i cyclically discharged into and withdrawn from the sai further space through the restricted passage.
• the present invention is based on the recognition tha when a differential of the type referred to abov differentiates the coupling or a member connected to it, which may be the restraint member, reciprocates linearl with respect to the cage perpendicular to the said axi and that the ends of the coupling or members connected t it, which may be the output shafts, reciprocate wit respect to the cage parallel to the said axis and tha one or more of the said reciprocating members may for one half of a piston/cylinder unit and that, if restricted passage is formed in either the piston o cylinder of the unit, fluid contained within the cylinde will be pumped through the passage which will generat pressure which resists differentiation of th differential.
• the fluid which is pumped back and forth by the piston cylinder unit(s) may be air but it is preferred that it is a liquid, such as oil, and in practice it may be an oil/air mixture.
• the further space into which the fluid is pumped may be outside the differential drive mechanism and may constitute, for instance, simply an oil sump. However, it is preferred that the further space is defined within the differential drive mechanism and that its volume increases as that of the associated cylinder decreases and vice versa.
• the restraint member is fixed relative to the cage, the coupling member is mounted to reciprocate in rotation about the restraint member and linearly parallel to the length of the restraint member, the coupling member including a tubular portion which extends around the restraint member and whose ends constitute annular pistons received in respective cylinders defined by the cage and the restraint member, the restricted passage constituting a bore within the restraint member extending substantially parallel to its length and two further bores which extend transverse to its length and connect the bore to respective cylinders.
• the coupling member is connected to move with the restraint member, the two ends of which constitute pistons within respective cylinders defined by the cage, the restricted passage comprising a bore within the coupling member which connects the two cylinders together.
• the ends of the coupling are restrained within the eccentric holes so as to be fixed parallel to the said axis, but nevertheless still rotatable about the axis of the holes, whereby when differential rotation of the output shafts occurs they reciprocate longitudinally, whereby the inner ends of the output shafts constitute pistons within cylinders defined by the cage.
• the restricted passage may then be formed through each inner end.
• a space may be provided within each output shaft and the restricted passage is formed in each output shaft which connects the associated space to the associated cylinder.
• the piston(s) inherently move with a generally sinusoidally varying speed in the associated cylinder(s) . This tends to result in the frictional torque and thus the torque bias ratio varying cyclically over each differential revolution.
• this cyclical variation is substantially smoothed by configuring the components so that the resistive force exerted by the oil and thus the torque bias ratio varies in a manner similar to that of a square wave rather than a sinusoidal wave.
• the torque bias ratio is dependent in part on the instantaneous value of the pressure generated in the fluid when differential rotation of the output shafts occurs, this may be effected by providing a variable restriction in or associated with the restricted passage which automatically varies the flow area of the restricted passage in inverse relation to the velocity of the fluid whereby, when the piston is moving the resistive force exerted by the oil is smoothed.
• This variable restriction may have a variety of forms but in one embodiment of the invention one end of the restricted passage is opposed to the surface of a member which moves relative to the restricted passage when differential rotation of the output shaft occurs, the said surface of the member having a profile which is so shaped that the spacing between the end of the restricted passage and said surface varies cyclically, whereby the resistance to flow presented by the restricted passage varies cyclically also.
• the restricted passage may include a variable restrictor valve member which is biased into contact with the surface of a member which moves relative to the restricted passage when differential rotation of the output shafts occurs, the said surface of the member having a profile which is so shaped that the position of the variable restrictor valve member moves relative to the restricted passage cyclically, whereby the resistance to flow presented by the restricted passage varies cyclically also.
• Figure 1 is a sectional view of the first embodiment of the invention
• Figure 2 is a similar view of the second embodiment
• Figure 3 is a similar view of the third embodiment
• Figure 4 is a sectional view at right angles to that of Figures 1 to 3 which shows the fourth embodiment on the right hand and a modification thereof on the left hand side;
• Figure 5 is a scrap sectional view on the line Z-Z in Figure 4.
• Figure 6 is a sectional view similar to Figure 3 of the fifth embodiment
• Figure 7 is an end view of the fifth embodiment from the left in Figure 6 with the portion on the line Z-Z in section;
• Figure 8 is a view similar to Figure 1 of the sixth embodiment
• Figure 9 is a sectional view on the line IX-IX in Figure 8.
• Figure 10 is a scrap sectional view on the line X-X in Figure 9.
• the differential of Figure 1 includes two output shafts 2 and 4, which are rotatable about a common axis 6 and pass through, and are rotatable with respect to, a cage 8 which is also rotatable about the axis 6.
• the cage has an end cover 9 which is the final drive flange through which rotational movement is transmitted to the cage.
• the output shafts At their inner ends the output shafts have a thickened portion 10 in which a cylindrical hole or recess 12 is formed, the axis 14 of which is parallel to but offset from the axis 6.
• Received in the holes 12 are the ends of a coupling bar 16 at whose centre there is a tubular portion 18 defining a hole whose axis is perpendicular to the axis 6. Slidably and rotatably received in this hole is a restraint bar 20.
• the ends of the restraint bar 20 are fixedly secured and sealed in respective holes in opposed sides of the cage 8.
• the coupling bar 16 carries part- spherical segments 22 whose surface engages the complementary internal surface of a respective sleeve 24 which is slidably received in the associated eccentric hole 12.
• each thickened portion 10 is of circular shape and is spaced by a clearance from the opposed circular portion of the internal surface of the cage, which is less than the clearance between the output shafts 2 at the point at which they pass through the cage, so that contact may not occur at that point.
• a sliding interface 23 is thus defined between each thickened portion and the cage.
• the tubular portion 18 of the coupling 16 is a close sliding fit between the outer surface of the restraint bar 20 and an opposed circular section portion of the inner surface of the cage 8 and seals 30 and 32 on the outer surface of the restraint bar 20 and the tubular portion 18 ensure a seal between the opposed sliding surfaces.
• Each end of the tubular portion 18 might thus be thought of as constituting an annular piston within an annular cylinder defined by the restraint 20 and the cage 8.
• an axial bore 34 which communicates with the interior of each cylinder by way of a respective small radial bore 36.
• the outer ends of the bore 34 are closed by respective seals 38.
• the force transmitted from the coupling bar to the thickened portions 10 is transmitted over the relatively large area of the external surface of the sleeves 24 and thus no excessively large contact loads are produced whereby wear of the cooperating surfaces of the sleeves 24 and thickened portions 10 is minimised.
• the contra-rotation of the output shafts results in the areas of contact between the thickened portions 10 and the internal surface of the cage contra-rotating also. This generates a frictional torque where both the normal force and the coefficient of friction are load dependent, which means that the torque bias ratio of the differential increases with increasing load.
• the embodiment of Figure 2 is generally similar but the bores 34, 36 have been omitted and the tubular portion 18 of the coupling 16 is shorter and does not form a sliding seal with opposed surfaces of the cage 8 or the inner ends 10 of the output shafts. Furthermore, the ends of the coupling bar 16 are not free to reciprocate within the eccentric holes 12 because the sleeves 24, whilst still free to rotate within the holes 12, are fixed in position, in this case by respective circlips 40. Nevertheless, linear reciprocation of the ends of the coupling bar 16 still occurs but in this case this is transmitted to the output shafts 4, 6.
• This embodiment is therefore suitable for applications, e.g. in a front wheel drive car, in which the outer ends of the output shafts are connected to universal joints or the like (not 12
• the oil is transferred or pumped cyclically through the bores 42 from one side of the inner ends 10 to the other, that is to say between the spaces in front of the inner ends 10 bounded by the output shafts, the cage, the coupling bar and the restraint bar and the spaces behind the inner ends 10 bounded by the output shafts and the cage.
• the sum of the volume of these spaces is of course always constant. The effect of this is the same as in the previous embodiment.
• FIG. 3 The embodiment of Figure 3 is again generally similar to that of Figure 1 but the coupling bar 16 is integral with the restraint bar 20 and the tubular portion 18 is thus not present.
• the cage 8 extends over the ends of the restraint bar 20 which are provided with annular seals 48 and are accommodated as a sealed sliding fit within complementarily shaped cylindrical recesses 50 defined by the cage.
• the restraint bar 20 is again provided with an 13
• the bore 3 is relatively large but accommodates a restrictor o throttle 52.
• the available volume of the cylinders 5 and the bore 34 are occupied by oil.
• each output shaft has a respective longitudinal hollow o bore 54 formed in it and the space which is occupied b the oil is constituted by the bore 54 and the space 5 behind the associated inner end 10 which is defined b the inner end 10, the associated output shaft and th cage.
• the space 56 is connected to the bore 54 by radial bore 58 in the wall of the output shaft.
• a piston 60 whose outer surface i engaged by one end of a compression spring 62 whose othe end is retained fixed by a circlip 64.
• the spring urge the piston 60 inwardly against the oil so that the space 54 and 56 are maintained full of oil at all times.
• the resistance to oil flow is increased and these increases are timed to occur at the four periods of minimum velocity of the piston (and in fact occur each time the linear or rotational speed of reciprocation of the coupling with respect to the cage is zero) and are dimensioned so that the variation in pressure of the oil within the cylinder is not generally sinusoidal but has a form approximating to that of a square wave, whereby variations in the oil pressure and thus in the torque bias ratio as the piston moves are reduced or smoothed.
• restrictor 52 has been omitted and the lower end of the bore 34 is closed by a seal 38 and the bore communicates at its lower end with the cylinder 50 by way of a restricted passage 60 which extends at an acute angle to the radial direction.
• a restricted passage 60 which extends at an acute angle to the radial direction.
• two vertical elongate, circumferentially spaced grooves or recesses 62 which are generally opposed to the outer end of the restricted passage 60.
• the recesses 62 constitutes a profiling of the surface of the lower cylinder 50 whose purpose is similar to that of the profiling 59 in Figure 5.
• the recesses 62 are dimensioned and positioned so that as the downstream end of the passage 60 moves linearly and in rotation it is opposed to one or other of the recesses 62 for most of each cycle but is partially obstructed by the cylinder wall at four separate times spaced apart by 90°. These times correspond to the periods of minimum speed of the pistons.
• the passage 62 is partially obstructed in this manner the resistance to oil flow through it is temporarily increased which leads to an increase in the torque bias ratio in the same manner and for the same purpose as that in Figure 5.
• Figures 8 to 10 show a further embodiment which is a modification of that shown in Figure 4 but also has the additional advantage of that shown in Figure 5 and also in Figures 6 and 7. In this case the restricted passage
• variable restrictor valve member 64 which is slidably accommodated in a bore 59 and in the peripheral surface of which an annular groove 68 is formed.
• the variable restrictor valve body 64 is biased 16
• valve body 64 projects out of the passage 58 varies cyclically and reaches four extreme values, i.e. maxima or minima per differential revolution.
• the flow resistance presented by the valve body 64 is at a minimum when the annular groove 68 is in line with the restricted passage 58.
• the minima in the flow resistance are timed to occur at the same times as in the preceding embodiments.
• the pistons form a substantial seal with the surface of the associated cylinder by virtue of their relative dimensions and preferably also the provision of one or more seals or piston rings.
• the restricted passage is connected and sealed at each end to the interior of a respective flexible bag or bellows of the type used in an aneroid within which the oil is contained and between which the oil is pumped through the restricted passage as the piston reciprocates. Since the oil is contained within a separately sealed space, a seal between the pistons and the associated cylinders is no longer necessary.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Retarders (AREA)
• Transmission Devices (AREA)

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• 1993
  • 1993-02-12 GB GB939302870A patent/GB9302870D0/en active Pending
  • 1993-09-13 US US08/120,977 patent/US5435210A/en not_active Expired - Fee Related
  • 1993-10-01 TW TW082108059A patent/TW242606B/zh active
• 1994
  • 1994-02-08 KR KR1019940002333A patent/KR0149455B1/ko not_active Expired - Fee Related
  • 1994-02-10 ZA ZA94921A patent/ZA94921B/xx unknown
  • 1994-02-11 AU AU60056/94A patent/AU6005694A/en not_active Abandoned
  • 1994-02-11 GB GB9515112A patent/GB2290360B/en not_active Expired - Fee Related
  • 1994-02-11 WO PCT/GB1994/000273 patent/WO1994018474A1/en active Application Filing

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