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
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/02—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts
  • F16H7/023—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts with belts having a toothed contact surface or regularly spaced bosses or hollows for slipless or nearly slipless meshing with complementary profiled contact surface of a pulley
• • 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
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/08—Means for varying tension of belts, ropes, or chains
  • F16H2007/0802—Actuators for final output members
  • F16H2007/081—Torsion springs
• • 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
  • F16H35/00—Gearings or mechanisms with other special functional features
  • F16H2035/003—Gearings comprising pulleys or toothed members of non-circular shape, e.g. elliptical gears

Definitions

• the present invention relates to a traction mechanism, which is intended as an assembly drive or as a control drive for an internal combustion engine.
• Said traction mechanism comprises a driven member and at least one driving member which are connected via a traction device, in particular an endless belt.
• the endless belt of the traction mechanism is prestressed by means of a tensioning device.
• Internal combustion engines normally have two separate traction mecha- nisms, one of which is a control drive, by means of which the crankshaft of the internal combustion engine drives the camshaft via which gas exchange valves of the internal combustion engine are actuated.
• the further traction mechanism, also designated as an assembly drive, of the internal combustion engine is intended for driving secondary assemblies, such as, for example, a water pump, air-conditioning compressor and alternator.
• DE 195 20 508 A1 shows a generic traction mechanism, in which a wheel or belt pulley assigned to the driving member or to the driven member has a nonround design.
• the wheel is provided with depres- sions distributed over the circumference, the number of depressions corresponding to the dominant order of torsional vibration or rotational movement of the internal combustion engine. Substantially audible vibration noises are to be eliminated by means of this known measure. Summary of the invention
• the object on which the present invention is based is, proceeding from the known solution, to implement a cost-optimized simplified construction of the traction mechanism.
• At least one belt pulley of the driving member or of the driven member of the traction mechanism has a nonround configuration.
• the vibration-damped traction mechanism which can thereby be achieved makes it possible to have a reduced width of the traction device designed particularly as an endless belt.
• the reduction according to the invention in the belt width of ⁇ 18% may be adopted, for example, for a conventional width design, according to the relationship,
• the traction mechanism according to the invention includes, furthermore, a tensioning device having a fixed component which is assigned a working eccentric acted upon by a spring means and connected to the tensioning roller.
• the invention includes adapting the prestressing force for the endless belt to the dynamics and the force peaks of the vibration-damped traction mechanism.
• the prestressing force can in this case be reduced by > 15%, this having advantageous effects on the useful life of the traction device and on the rolling bearings, for example belt pulleys, of the assemblies which are connected to the traction mechanism.
• the reduced prestressing force of the traction device has a direct influence on the work of friction, in particular during the action of run-in and run-out of the toothing of the toothed belt with respect to the toothing of the belt pulley.
• the reduced prestressing force established in the vibration- damped traction mechanism advantageously reduces the work of friction between the tooth flanks of the toothed belt and the belt pulley in each case during the run-in and run-out actions, which at the same time has an advantageous effect on the wear of the traction device.
• the re-zad work of friction reduces the risk of tooth jump which, in the control drive of the internal combustion engine, leads to adverse consequential damage and may bring about a complete failure of the internal combustion engine.
• the findings gained from the vibration-damped or stabilized traction mechanism are utilized to achieve a design of the traction mechanism which is optimized in terms of overall space and also cost-optimized.
• An object-compatible solution to the set problem on which this invention is based is achieved by means of a belt pulley configured as an ellipse.
• This ellipse is preferably designed such that the smallest axis "a” is in the ratio of > 1 : 1.1 with respect to the largest axis "b".
• the ratio of 1 : 1.3 of the axes "a" to "b” is considered as the upper limit value.
• the invention includes configuring the nonround belt pulley as a symmetrical or asymmetric polygon with rounded transitions.
• the profile of the belt pulley is determined by means of a calculation in conjunction with a simulation or by means of tests.
• the result of the vibration-damped traction mechanism according to the invention is that the fluctuation occurring in the prestressing force or in the force peaks of the endless belt is markedly reduced over the entire rotational speed spectrum in the operating state of the internal combustion engine. Proceeding from an average value of the traction force, the prestressing force, the fluctuation in the force peaks as far as an upper load or a lower load can be advantageously reduced to a value of > 50% by means of the measures according to the invention.
• the vibration-damped traction mechanism according to the invention makes it possible to use endless belts with narrow dimensioning, in conjunction with adapted belt pulley widths. Both measures advantageously make it possible to reduce the required overall space of the traction mechanism. Owing to the endless belt of narrower design and to the re- prised prestressing force of the traction device, there is the further result of simple mounting.
• the design of the endless belt makes it possible to vary the number and/or the arrangement of the rein- forcements designed as pull cords, as compared with previous endless belts.
• the endless belt adapted to the reduced prestressing force of the traction device of the traction mechanism according to the invention may, for ex- ample, have a reduced number of pull cords.
• the pull cords are preferably embedded in an HNBR rubber mixture.
• the endless belt has a polyamide fabric on the inside.
• the endless belt provided for the traction mechanism according to the invention includes pull cords made from high-purity glass or from carbon cord. These materials make it possible to further reduce the number of pull cords, a high elasticity or bending strength at the same time remaining ensured. Moreover, this reinforcement improves the deformation behavior and the associated intrinsic heating, with the result that a prolonged useful life of the traction device can be achieved.
• the vibration-damped traction mechanism according to the invention in conjunction with a reduced tractive force, also gives rise to a reduced load per unit area of the traction device.
• a traction device adapted to the reduced tractive force can be produced more cost-effectively, the width remaining unchanged, in that cost-effective reinforcements, pull cords, are employed.
• the use of an unchanged traction device in a vibration-damped traction mechanism brings about a markedly increased useful life.
• endless belts of narrow design which are optimized in terms of overall space and in which high-strength pull cords made from carbon cord or high-purity glass are integrated as reinforcement.
• figure 1 shows the construction of a traction mechanism according to the invention
• figure 2 shows a graph illustrating the tractive force of a conventional traction mechanism in comparison with a vibration-damping traction mechanism
• figure 3 shows a detail of the traction mechanism according to figure 1, illustrating the tooth meshing between a toothed belt and a toothed belt pulley;
• figure 4 shows the construction of the traction device according to the invention
• figure 5 shows a sectional illustration of a tensioning device of the traction mechanism depicted in figure 1.
• Figure 1 shows a traction mechanism 1 of an internal combustion engine, further details of which are not illustrated.
• the driven member 2 is provided by a toothed belt pulley 3 which is connected fixedly in terms of rotation to a crankshaft, not depicted in figure 1, of the internal combustion engine.
• the traction mechanism 1 serves for driving a camshaft, a driving member 4, which is provided with a toothed belt pulley 5.
• the traction device 6 provided is an endless belt which is designed as a toothed belt and which at least partially surrounds the toothed belt pulleys 3, 5.
• the traction mechanism 1 serves, moreover, for driving a further driving member 7, for example a water pump.
• the traction device 6 is guided correspondingly at the toothed belt pulley 8 of the driving member 7.
• the traction mechanism 1 On an idle side of the traction mechanism 1 rotating clockwise, adjacent to the toothed belt pulley 5, the traction mechanism 1 is assigned, furthermore, a tensioning device 9, the tensioning roller 10 of which, acted upon by spring force, is supported on the outside on the traction device 6. Moreover, the traction device 6 is guided at a deflecting roller 11 between the tensioning device 9 and the toothed belt pulley 3.
• the driven member 2 the toothed belt pulley 3 has a nonround design.
• the toothed belt pulley 3 is identified by the two axes "a" and "b", the length of the axis "b” exceeding the length of the axis "a”.
• the nonround toothed belt pulley 3 gives rise to a vibration-stabilized traction mechanism 1 , thereby avoiding adversely high force peaks in the traction device 6 which has a correspondingly adapted dimensioning. Moreover, the vibration-stabilized traction mechanism 1 makes it possible to use a simple tensioning device 9 in order to implement a prestressing of the traction device 6 which is sufficient for the operating state. Details of the embodiment according to the invention of the toothed belt pulley 3 and also the traction device 6 and tensioning device 9 are illustrated in figures 3 to 5.
• Figure 2 shows a graph which, in a comparison, illustrates the profile of the prestressing force of the traction device 6 of a previous traction mechanism in relation to a traction mechanism according to the invention.
• the prestressing force is plotted on the ordinate and the rotational speed of the internal combustion engine is plotted on the abscissa.
• the two curved profiles spaced apart radially correspond to a bandwidth of the prestressing force occurring in the operating state of the internal combustion engine.
• the curved profiles I are in this case assigned to a traction mechanism of previous type of construction.
• the further curved profiles II can be implemented by means of the measure according to the invention, illustrated in figure 1, which includes a toothed belt pulley 3 of nonround design.
• the measure according to the invention gives rise to a stabilized traction mechanism, with a re- 9d level of the force peaks occurring, that is to say the fluctuation width occurring between the limit values, the upper force and the lower force, is advantageously decisively reduced. Consequently, over the entire rotational speed spectrum of the internal combustion engine, a fluctuation of the prestressing force of ⁇ 50% is established, that is to say toward the upper force or the lower force, starting from an average value "M".
• the maximum value "A" occurring between the upper force and the lower force in this case differs markedly from the value "B" of previous traction mechanisms.
• Figure 3 shows a detail of the traction mechanism 1 according to figure 1 and in this case illustrates a run-in of the traction device 6 on the toothed belt pulley 3 of nonround configuration.
• the work of friction between an internal toothing 12 of the traction device 6 and an external toothing 13 of the toothed belt pulley 3 decreases at the same time.
• the work of friction arises in the event of a sliding movement of a tooth flank 14 of the internal toothing 12 of the traction device 6 on an associated tooth flank 15 of the toothed belt pulley 3 between a first con- tact phase, which corresponds to the position "a", and the reaching of an end position in the position "b".
• the reduced work of friction in the contact zone between the traction device 6 and the toothed belt pulley 3 due to the decreased prestressing force of the traction device 6 results in a reduced frictional heat on account of the reduced deformation of the traction device 6, which has an advantageous effect on the wear of the traction device 6 and as a result of which, overall, a prolonged useful life of the traction mechanism 1 can be achieved.
• the construction of the traction device 6 according to the invention is shown in figure 4.
• the width "S" of the traction device 6 can be reduced.
• the width of the toothed belt pulley 3, 5, 8 and also the tensioning roller 10 and the deflecting roller 11 can be reduced, this having an advantageous effect on the acquired overall space of the traction mechanism 1.
• the construction of the traction device 6 provides continuous pull cords 16 which are arranged in parallel and are embedded in an HNBR rubber mixture 17.
• the internal toothing 12 of the traction device 6 has a polyamide fabric 18. As a measure for increasing the tearing strength of the traction device 6 or for optimizing the width "S" of the traction device 6, it is appropriate to use pull cords 16 made from high-purity glass or carbon pull cords 16.
• the tensioning device 9 also to be designated as a simple eccentric, comprises a cylin- drically designed carrying body 19 which is fastened fixedly, for example to a housing 21 of the internal combustion engine, by means of a screw connection 20.
• the carrying body 19 is connected to a baseplate 23 which is supported on the housing 21 and is fixed in terms of rotation to the latter.
• a working eccentric 22 arranged rotatably on the carrying body 19 is a working eccentric 22, on which is positioned a rolling bearing 25 which is surrounded on the outside by the tensioning roller 10.
• a spring means 24 arranged between the baseplate 23 and the working eccentric 22 gives rise, in the in- stallation state of the tensioning device 9, to a nonpositive bearing contact of the tensioning roller 10 against the traction device 6.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)

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• 2005
  • 2005-05-12 BR BRPI0511790-9A patent/BRPI0511790A/pt not_active IP Right Cessation
  • 2005-05-12 WO PCT/EP2005/005108 patent/WO2005119087A1/en not_active Application Discontinuation
  • 2005-05-12 EP EP05747367A patent/EP1756448A1/de not_active Ceased

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