EP1756448A1 - Cost-optimized traction mechanism - Google Patents

Cost-optimized traction mechanism

Info

Publication number
EP1756448A1
EP1756448A1 EP05747367A EP05747367A EP1756448A1 EP 1756448 A1 EP1756448 A1 EP 1756448A1 EP 05747367 A EP05747367 A EP 05747367A EP 05747367 A EP05747367 A EP 05747367A EP 1756448 A1 EP1756448 A1 EP 1756448A1
Authority
EP
European Patent Office
Prior art keywords
traction
traction mechanism
belt pulley
toothed belt
traction device
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
EP05747367A
Other languages
German (de)
French (fr)
Inventor
Rainer Pflug
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
IHO Holding GmbH and Co KG
Original Assignee
Schaeffler KG
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
Priority claimed from DE200410027055 external-priority patent/DE102004027055A1/en
Application filed by Schaeffler KG filed Critical Schaeffler KG
Publication of EP1756448A1 publication Critical patent/EP1756448A1/en
Ceased legal-status Critical Current

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
    • 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)

Abstract

The present invention relates to a traction mechanism (1), comprising a driven member (2) and at least one driving member (4) which are connected via a traction device (6) designed as a toothed belt. To achieve a vibration-damped traction mechanism (1), the driven member (2) designed as a toothed belt pulley (3) has a nonround configuration.

Description

Cost-optimized traction mechanism
Field of the invention
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.
Background of the invention
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.
On account of the rotational nonuniformity of the internal combustion engine, torque fluctuations associated with changes in angular speed or in rotational speed are introduced into the traction mechanisms and lead to increased wear, in particular of the traction device. The mechanical vibration excitations associated with this lead, in resonant ranges, to unpleasantly audible noises. This entails, furthermore, increased frictional forces which are detrimental to the useful life of the traction mechanism, in particular of the traction device. 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. For this purpose, 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.
The solution to this set problem lies in a combination of the following measures. 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,
Rb(belt width)= Fh(belt peak load)/Ze(number of meshed teeth)/Rj(specific belt coefficient)
Example calculation: Fh = 3000 N; Zθ = 13.2; Rj = 6 N / mm / Ze Rb = 3000/13.2/6 Rb = 37.8 mm The required belt width Rb is 38 mm. Proceeding from this value, the belt width can be reduced by the value > 18% by means of the measures according to the invention.
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.
By virtue of the measures which stabilize the traction mechanism, that is to say dampen vibrations, in the form of a nonround belt pulley preferably assigned to the crankshaft, clear reduced dynamics and, along with this, reduced force peaks of the traction mechanism are established. Advantageously, as a result, individual components of the traction mechanism can be simplified, thus resulting in a cost benefit and in a reduced overall vol- ume of the traction mechanism.
The invention includes adapting the prestressing force for the endless belt to the dynamics and the force peaks of the vibration-damped traction mechanism. By virtue of the measures according to the invention, 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. Moreover, according to the invention there is provision for adapting the width of the endless belt to the dynamics or the force peaks of the traction mechanism. It is appropriate in this case to reduce the width by > 18%, as compared with conventional traction mechanisms, with the boundary conditions being the same, that is to say with the internal combustion engine being the same, and with the torque being identical.
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. Moreover, the re- duced 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.
Consequently, according to the invention, 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.
Further advantageous embodiments of the invention are the subject matter of the dependent claims 2 to 10.
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". Tests for many applications, that is to say conventional internal combustion engines, made it possible to determine an optimum axis ratio of 1 : 1.3 to achieve a vibration-damped traction mechanism. The ratio of 1 : 1.3 of the axes "a" to "b" is considered as the upper limit value.
It is appropriate, furthermore, to assign a belt pulley of polygon-like design to the driving member or the driven member of the traction mechanism. Moreover, the invention includes configuring the nonround belt pulley as a symmetrical or asymmetric polygon with rounded transitions.
Regardless of the respective geometric configuration or design, 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- duced prestressing force of the traction device, there is the further result of simple mounting.
Due to the reduced prestressing forces, 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. Furthermore, in the region of an inner profiling or inner toothing, the endless belt has a polyamide fabric on the inside.
Preferably, 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. Alternatively, it is possible to use 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. Brief description of the drawings
The invention is illustrated in figures which explain individual components in more detail. In the figures:
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.
Detailed description of the drawings
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. 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.
To achieve a vibration-damped traction mechanism 1 , the driven member 2, the toothed belt pulley 3, has a nonround design. The toothed belt pulley 3, preferably designed as an ellipse, compensates, for example, the adverse vibrations introduced into the traction mechanism 1 by the internal combustion engine and occurring on account of the rotational nonuni- formity of the internal combustion engine. To illustrate the ellipse, 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. In the graph, 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. As the graph according to figure 2 shows, the measure according to the invention gives rise to a stabilized traction mechanism, with a re- duced 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. Owing to the advantageous reduced prestressing force according to the invention of the traction device 6, 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. Advantageously, on account of the toothed belt pulley 3 of nonround configuration and the associated reduced prestressing force of the traction device 6, the width "S" of the traction device 6 can be reduced. Correspondingly to the width "S" of the traction device 6, 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.
Details of the tensioning device 9 are illustrated in figure 5. 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. In this case, 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. 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.
Reference numerals
traction mechanism driven member toothed belt pulley camshaft toothed belt pulley traction device driving member toothed belt pulley tensioning device tensioning roller deflecting roller internal toothing external toothing tooth flank tooth flank pull cord rubber mixture polyamide fabric carrying body screw connection housing working eccentric baseplate spring means rolling bearing

Claims

Patent Claims
1. A traction mechanism, which is intended as an assembly drive or as a control drive for an internal combustion engine, comprising a driven member (2) and at least one driving member (7) which are connected via a traction device (6), in particular a toothed belt configured as an endless belt, the traction device (6) being prestressed by a tensioning device (9), wherein, to achieve a vibration-damped traction mechanism (1), a belt pulley or toothed belt pulley (3, 5) of the driven member (2) and/or at least one belt pulley or toothed belt pulley of the driving member (7) has a non- round configuration, a width "S" of the traction device (6) being designed to be narrower by ≥ 18% in comparison with previously designed traction mechanisms, and the tensioning device (9) preferably comprising a fixed component which is assigned a working eccentric (22) acted upon by a spring means and connected to a tensioning roller (10).
2. The traction mechanism as claimed in claim 1, the belt pulley or toothed belt pulley (3) of nonround configuration being shaped as an ellipse.
3. The traction mechanism as claimed in claim 2, wherein the belt pulley or toothed belt pulley (3) configured as an ellipse has a ratio of the smallest axis (a) to the largest axis (b) of > 1 : 1.1.
4. The traction mechanism as claimed in claim 1 , wherein the traction device (6) designed as an endless belt is guided on a toothed belt pulley (3) of polygon-like configuration.
5. The traction mechanism as claimed in claim 1, which includes at least one nonround toothed belt pulley (3) designed as a symmetrical or asymmetric polygon and having rounded transitions.
6. The traction mechanism as claimed in claim 1 , a permissible fluctuation (A) or force dispersion of a prestressing force (F) of the traction device (6) in an enveloping curve between an upper load and a lower load over a rotational speed spectrum of the internal combustion engine amounting to < 50%.
7. The traction mechanism as claimed in claim 1, the traction device (6) including as reinforcement pull cords (16), the number and/or construc- tion of which differ with respect to previous traction devices.
8. The traction mechanism as claimed in claim 7, the traction device (6) having a reduced number of pull cords (16) which are embedded in an elastomer or HNBR rubber mixture (17).
9. The traction mechanism as claimed in claim 7, an internal toothing (12) of the traction device (6) having a polyamide fabric (18).
10. The traction mechanism as claimed in claim 1, the traction device (6) including as reinforcement pull cords produced from high-purity glass and carbon cord.
EP05747367A 2004-06-03 2005-05-12 Cost-optimized traction mechanism Ceased EP1756448A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE200410027055 DE102004027055A1 (en) 2004-06-03 2004-06-03 Traction mechanism for use in internal combustion engine, has driven and driving units that are provided with respective toothed belt pulley, where one of the pulleys has ellipse configuration with a preset width
US59235204P 2004-07-29 2004-07-29
PCT/EP2005/005108 WO2005119087A1 (en) 2004-06-03 2005-05-12 Cost-optimized traction mechanism

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EP1756448A1 true EP1756448A1 (en) 2007-02-28

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JP5205387B2 (en) 2006-10-09 2013-06-05 ザ ゲイツ コーポレイション Synchronous belt drive system
CN101772659A (en) * 2007-05-31 2010-07-07 亨利·D·布朗森 Reciprocating belt drive
WO2013142951A1 (en) 2012-03-29 2013-10-03 Litens Automotive Partnership Tensioner and endless drive arrangement
JP7003119B6 (en) 2016-09-13 2023-08-18 リテンズ オートモーティヴ パートナーシップ V-tensioner and endless drive

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WO2005119087A1 (en) 2005-12-15

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