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
  • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
  • F16H55/32—Friction members
  • F16H55/52—Pulleys or friction discs of adjustable construction
  • F16H55/56—Pulleys or friction discs of adjustable construction of which the bearing parts are relatively axially adjustable

Definitions

• the invention relates to an adjustable pulley, in particular for a continuously variable transmission or CVT, provided with two sheaves having a central opening into which an axle of the pulley is inserted, a first sheave of which is fixedly connected to the pulley axle and a second sheave of which is displaceable in the axial direction along the pulley axle by means of the operating means of the pulley.
• a pulley of this type is, for example known from US patent no. 6,012,998 and is especially used in CVTs of passenger motor vehicles in particular.
• two pulleys are used having a drive belt between them, which drive belt is clamped between the two sheaves of the two pulleys during operation by in each case moving, that is to say, at least pushing, said second or displaceable sheave in the axial direction towards said first or fixed sheave by means of the operating means.
• the clamping forces exerted on the drive belt by the respective operating means via the sheaves in this case determine the radial positions of the drive belt between these sheaves of the two pulleys and thus for the transmission ratio of the CVT.
• said clamping forces determine the maximum torque which can be transmitted between the two pulleys, that is to say determine the maximum frictional force which can be exerted between the drive belt and the sheaves of a respective pulley.
• the automotive industry aims for low production costs.
• the pulleys in particular are relatively complex and heavily dimensioned components which thus to a large degree determine the cost price of the overall CVT.
• the invention relates to a new pulley construction which can advantageously be produced less expensively than the constructions which are currently known. More particularly, a number of components of the pulley according to the invention can be produced and/or assembled in a simpler manner than was previously possible. In a particularly advantageous embodiment of the pulley according to the invention, the latter even has fewer components than the known pulley.
• the axial cross section of the central opening of the fixed pulley sheave is non-circular and the pulley axle is provided with an axial cross section which is substantially identical in shape thereto, at least where the fixed sheave is situated on the axle, and the fixed sheave is fitted on the axle by a force fit.
• the central opening of the fixed sheave follows a regular polygon having four or more rounded corners and having at least slightly convexly curved sides in between.
• a shape can be produced relatively easily and results in an optimum form-fit and force fit between the sheave and the axle.
• the assembly of the fixed sheave and the axle takes place either by - first heating the fixed sheave and/or cooling the axle, by then inserting the axle into the central opening of the fixed sheave, and finally by bringing the two components to the same and/or ambient temperature, or by
• the (axially) displaceable sheave is fixedly (non-rotatably) connected to the axle by means of a key/groove connection in the tangential or peripheral direction so that the torque can be transmitted between them.
• a key/groove connection in the tangential or peripheral direction so that the torque can be transmitted between them.
• the "key of the known key/groove connection is usually provided as a separate component or components, for example in the shape of a cylindrical pin or a number of (bearing) balls.
• the axle has to have an axial cross section at the location of the displaceable sheave which is smaller than, but substantially identical in shape to the opening of the displaceable sheave and thus preferably substantially identical in shape to the opening of the fixed sheave.
• Fig. 1 diagrammatically shows a cross section of the continuously variable transmission with two adjustable pulleys according to the prior art
• Fig. 2 diagrammatically shows a cross section of a primary pulley according to the prior art
• Fig. 3 diagrammatically shows a cross section of a first exemplary embodiment of the adjustable pulley according to the invention at the location of the fixed sheave thereof and oriented in the axial direction;
• Fig. 4 diagrammatically shows a cross section of the first exemplary embodiment of the adjustable pulley according to the invention at the location of displaceable sheave thereof and oriented in the axial direction;
• Fig. 5 diagrammatically shows a cross section of a second exemplary embodiment of the adjustable pulley according to the invention.
• the continuously variable transmission 1 according to the prior art shown diagrammatically and in cross section in Fig. 1 is provided, in a transmission housing 11 thereof, with a so-called primary adjustable pulley 3 and a so-called secondary adjustable pulley 7.
• the pulleys 3, 7 each comprise two sheaves 4, 5; 8, 9 which are fitted on a primary axle 2 and a secondary axle 6, respectively.
• One sheave 5; 8 of each pulley 3; 7 is axially displaceable, as a result of which the radial position of the drive belt 10 between the pulleys 3 and 7 can be modified and the transmission ratio can be adjusted, while the respective other fixed sheave 4; 9 is fixedly connected to the respective axle 2; 6, both axially and tangentially.
• Each of the displaceable sheaves 5 and 8 is provided with the operating means of the respective pulley 3, 4 in the form of a piston/cylinder assembly, with the displaceable sheave 8 of the secondary pulley 4 being provided with a single piston/cylinder assembly 26, 27 and with the displaceable sheave 5 of the primary pulley 3 being provided with a double piston/cylinder assembly.
• the double piston/cylinder assembly of the primary pulley 3 comprises two cylinder chambers 13, 14.
• a first cylinder chamber 13 is enclosed by the cylinder 19, the piston 18, the radial wall 24 and the axle 2.
• a second cylinder chamber 14 is enclosed by the cylinder 21 , the piston 17, the sheave 5 and the sleeve 20 of the primary axle 2 on which the displaceable sheave 5 is fitted.
• fluid can be introduced into and removed from said cylinder chambers 13, 14 and/or the volume thereof can be increased or decreased, with the displaceable sheave 5 with the sleeve 20 being displaced in the axial direction along the primary axle 2.
• axles 2, 6 are mounted in the transmission housing 11 with in each case two bearings 49, 52 per axle 2; 6, at least one bearing 49 of which is attached to the respective axle 2 or 6 by means of a nut 53 on an axial end 55 of said axle 2 or 6.
• the primary pulley 3 known from US-6,012,998 is illustrated in Fig.2 in cross section.
• the fixed sheave 4 of the primary pulley 3 is arranged on the axle 2 thereof as a separate component.
• the fixed sheave 4 is placed against steps 33 and is thus fixed in said direction.
• the steps 33 are formed by the stepwise increase in the (outer) diameter of the axle 2.
• the fixed sheave 4 is fixed on the axle 2 either by an adhesive or by means of a key/groove connection.
• the fixed sheave 4 is by contrast fixed on the axle 2 by means of at least one polygonal force fit, as is diagrammatically illustrated in Fig.
• the periphery of the (unloaded/separate) axle 2 in this case has an oversize in the range from 0.005 mm to 0.050 mm compared to the periphery of the central opening of the (unloaded/separate) fixed sheave 4.
• the radial oversize in the radial direction is in this case less than 0.025 mm and, for example, has a value between 0.015 mm and 0.020 mm.
• a small radial oversize the attendant small degree to which the material has to be pressed and the unexpectedly low internal stresses during operation appear to have become possible by said additional tangential fixation of the form-fit between the fixed sheave 4 and the axle 2.
• the radial oversize according to the invention has to be greater than 0.025 mm, preferably greater than 0.035 mm.
• the axial cross sections of the axle 2 and of the central opening of the fixed sheave 4 are substantially identical in shape and in this case substantially form a quadrangle having rounded corners and convex sides.
• said corners at least approximately form an arc of a circle, the radius Rh of which is between 1 mm and 10 mm and said sides at least approximately form an arc of a circle, the radius Rz of which is greater than 10 mm and is preferably between 50 mm and 100 mm.
• the polygonal shapes generally used in the art for such a form-fit have a continuously variable radius of curvature, in which case the abovementioned arcs and radii are only approximations.
• said bevel or rounding of a dimension provided in the axial direction is 0.5 to 2.5 mm and is preferably formed by an arc of a circle having a radius of 10 to 50 mm and merges smoothly with the contour of said central opening.
• the displaceable sheave 5 is preferably also fixed on the axle 2 by means of a polygonal form-fit, at least only in the tangential direction, as is diagrammatically illustrated in Fig.4 by means of an axial cross section of the primary pulley 3 at the location of the displaceable sheave 4 thereof.
• some clearance is left between the periphery of the axle 2 and the periphery of the central opening of the displaceable sheave 5 which, measured in the radial direction, in any case has to be smaller than 0.050 mm and is preferably smaller than 0.025 mm, more particularly has a value between 0.010 mm and 0.020 mm.
• the axial cross sections of the axle 2 and of the central opening of the displaceable sheave 5 are substantially identical in shape and in this case substantially form a quadrangle having rounded corners and convex curved sides.
• Fig. 5 diagrammatically shows a second exemplary embodiment of the adjustable pulley 7 according to the invention viewed in the radial direction and in cross section. This is the secondary pulley 7, the axle 6 of which is (at least in this example) on its left-hand side provided with a gear wheel 56 which is integrally formed therewith.
• the two pulley sheaves 8, 9 are therefore successively moved and/or pushed over said gearwheel 56 from the right-hand end of the axle 6. More particularly, the piston 26 of the piston/cylinder assembly 26, 27 of the secondary pulley 7 is moved over the axle 7 before the sheaves 8, 9, which piston 26 is clamped in the respective cylinder 27 between a first step 57 of the axle 7 and a spring 58 provided for this purpose.
• both the central opening of the fixed sheave 9 and the axle 7 are provided at the location of said fixed sheave 9 with a second step 59 which forms a mechanical stop in the axial direction for the fixed sheave 9 and, together with the bearing 49, locks the latter in the axial direction, so that said force fit between the axle 7 and the fixed sheave 7 is also relieved in said direction and/or ensures mutual fixation.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Transmissions By Endless Flexible Members (AREA)
• Pulleys (AREA)

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Citations (8)

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• 2008
  • 2008-12-12 NL NL2002325A patent/NL2002325C2/nl not_active IP Right Cessation
• 2009
  • 2009-12-11 JP JP2011540620A patent/JP5653361B2/ja not_active Expired - Fee Related
  • 2009-12-11 EP EP09771602.1A patent/EP2376809B1/en not_active Not-in-force
  • 2009-12-11 CN CN200980149901.4A patent/CN102245937B/zh not_active Expired - Fee Related
  • 2009-12-11 WO PCT/NL2009/000250 patent/WO2010068091A1/en not_active Ceased

Patent Citations (8)

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