DE10325701A1 - Toothed wheel transmission has interengaging cogged wheels wherein operating engagement angle of teeth is less than fourteen degrees - Google Patents

Abstract

Gear transmission, in which two toothed gear bodies (1, 4) interlocking with a predetermined tooth flank play are subjected to a change in position transversely to their axis of rotation and a dynamic alternating stress during operation, which change the tooth flank play, the operating pressure angle (α _wtθ ) of the toothing (2, 3 ) is less than 14 ° to minimize the influence of the position change on the backlash.

Description

The Invention relates to a gear transmission according to the preamble of Claim 1 and use of a gear transmission in steering wheel drives in internal combustion engines according to claim 8.

to power transmission Gearwheels are often used in machines and systems. A characteristic of the gearbox is the presence of backlash to avoid jamming of the teeth. This backlash must be in be able to make manufacturing deviations of the wheel body, the toothing, the relative Location of the wheel center to each other due to shaft and axis tolerances, center distance tolerances (Hole positions), elastic deformations and the movement of the gears and balance waves within their camp play.

hereby there is a minimum backlash, as a result of which it takes off the tooth flanks and stops on the opposite flank, also referred to as "hammering" can, especially with non-uniform operated machines with rotary path excitation or changing start and stop Output torques, i.e. with dynamic alternating stress. The Running through the backlash caused in gear transmissions with increasing games increasingly undesirable noises and additional, jerky Loads in the shoot. For example, hammering gears in crankcases Gray cast iron dynamic load increases in Range from 10 to 35%. In the steering wheel drive of a commercial vehicle engine can dynamic peak loads occur at nominal play, which are up to 25% are higher than with a zero backlash reference system. The increase of backlash accordingly expect significantly increasing load impacts.

Become different materials for gears and casing used, so changes this backlash with evenly changing temperature of gear and housing structure. For example, the gears are made of a steel material and the gearbox made of an aluminum material, so takes under the influence of different Coefficient of thermal expansion of the Steel material and aluminum the backlash with increasing Temperature too. The lowest temperature at which the gear transmission is stuck Must work, thus determines the minimum backlash that is required for the design the toothing must be taken into account is. This is often one very low starting temperature of the machine. If the machine is then over a operated wide temperature range, so it turns out clearly higher CTE of the housing compared to the gear a significantly higher backlash.

Either a dynamic alternating stress, e.g. in the form of jerky Loads due to torsional vibration excitation and changing external output torques, as well as different thermal expansions of the housing and Gears are typical features of timing drives in internal combustion engines. Out the mentioned, undesirable Effects results in the endeavor to change the backlash in gear transmissions as a result of the radial change in position of the wheel bodies relative to one another in operation, in particular due to different thermal expansion different housing and gear materials at different temperatures and through the wheel body movements to minimize within the camp game.

Numerous constructive solutions for fully compensating the backlash and compensating for the backlash change in gear transmissions are known, among other things: two axially arranged gear halves that are tangentially braced against one another, for example by means of elastomers, springs, or hydraulic actuators, and with a driven flank and back flank of a counter gear at the same time are in contact; Gears with slightly tapered teeth (taper angle 1:30 to 1:10) and axial infeed; Radial infeed of a gearwheel of a single pair of wheels; two axially successively arranged gear stages, which are braced against each other, so that each gear stage can be assigned a torque direction; Gear stages with an intermediate wheel mounted in at least two handlebars or cassettes, cf. eg DE 6 14 431 and DE 37 08 149 C1 ; Wheel body slotted in the tooth base, which due to the tangential resilience of the individual tooth can cushion changes in backlash caused by tolerance, play and elasticity almost without jamming.

Indeed take additional constructive measures Construction effort after itself. In addition, the arrangement of intermediate gears in additional Handlebars / cassettes additional Junctions and games in the flow of power. The number of handlebars and especially the playful bearings and connection points of Handlebar to housing or gear and the two handlebars with each other is the cause of the very low rigidity of such a transmission.

In the case of tangential infeed of two wheel halves, high alternating load portions lead to a significant increase in the overall width, since both gear wheel halves have to transmit approximately the same torque, which is the case in critical installation space situations can not be realized. A complete compensation is only possible with end wheels, not with intermediate wheels. With axial infeed, increased installation space is also necessary due to the axial displacement path and the infeed mechanism. The radial infeed of a gear is only suitable for one end wheel and also requires the shaft to be moved radially (change in center distance).

In the DE 39 06 639 A1 describes a gear body slotted between all teeth in the tooth base, which due to the elasticity of the individual teeth in the tangential direction can cushion the tolerance, play and elasticity-related change in the tooth engagement condition almost without jamming. The compensation of the tooth flank play is associated with a significant increase in the normal forces on the tooth flank in the case of larger changes in the center distance. Only low torques can be transmitted.

The The invention is therefore based on the object of a gear transmission according to the preamble of claim 1, in which the influence is radial change of position the wheel center relative to each other is minimized on the backlash without the increase constructive effort.

This Task becomes according to the characteristics of the characteristic part of claim 1 solved.

hereby a gear transmission is created in which two intermeshing toothed wheel center, that in the operation of a dynamic alternating stress and a radial change in position are, have an operating pressure angle less than 14 °.

The small operating pressure angle minimizes the influence of radial change of position the wheel center relative to each other on the backlash. The radial change of position the wheel center can be functionally intended, vibrationally dynamic, tolerant and / or due to bearing play, but in particular also due to heat, if housing material and gear material different thermal expansion coefficients to have. The design effort is low because only the tooth profile is trained accordingly.

Especially the gear mechanism effectively counteracts hammering in an internal combustion engine, of materials with different coefficients of thermal expansion comprises the because of the big one Temperature range from typically -40 to + 140 ° C to one huge radial change of position the wheel center to lead.

Further becomes a use of the gear transmission in timing gear drives created in internal combustion engines.

Further Embodiments of the invention are the following description and the dependent claims refer to.

The Invention is illustrated below with reference to the accompanying figures gene illustrated embodiments explained in more detail.

1 shows two interlocking toothed wheel bodies.

2 shows the face and operating pressure angle of a toothing.

3 shows backlash of two gear pairs made of steel in an aluminum housing with individual parts.

4a . 4b and 4c each show a portion of an interlocking toothing of two wheel bodies with different operating pressure angles.

in die Verzahnung 3 eines beabstandeten Radkörpers 4 ein. Dargestellt sind ferner der Grundkreisdurchmesser d_b, der Fußnutzkreisdurchmesser d_Nf, die Wälzkreistangente 5 sowie die Betriebseingriffslinie 6.The in 1 wheel body partially shown 1 an optionally multi-stage gearbox, which is expediently mounted in a housing, in particular a control gearbox for an internal combustion engine, engages with its toothing 2 at an operating pressure angle

in the gearing 3 a spaced wheel body 4 on. Also shown are the base circle diameter d _b , the root circle diameter d _Nf , the pitch circle tangent 5 as well as the operational intervention line 6 ,

entspricht dabei wie in 2 dargestellt einem Abstand

der beiden Radkörper 1, 4 bei einer Temperatur

, der einen Versatz gegenüber dem Abstand α_d der Nennverzahnung aufweist. Durch die Verschiebung der Grundkreise r_b1 und r_b2 ergibt sich zudem eine Abweichung der Betriebseingriffsline 6 von der Stirneingriffslinie 7.The operating pressure angle

corresponds as in 2 represented a distance

of the two wheel centers 1 . 4 at a temperature

, which has an offset from the distance α _{d of} the nominal toothing. The displacement of the basic circles r _b1 and r _{b2 also} results in a deviation of the operational intervention line 6 from the forehead line of intervention 7 ,

The wheelbase center distance 1 . 4 and the shape of the gears 2 . 3 determine a nominal backlash. Due to the manufacturing and assembly-related tolerances regarding the center distance, the toothing and other components of the gearbox, the bearing play and the different thermal expansion of the wheel body and possibly the housing, a different backlash can occur during operation, which can cause the gearbox to hammer ,

.The minimum and maximum backlash j _tmin , j _{tmax of} the toothing 2 . 3 can be calculated according to DIN 3967 taking into account the individual parts. The individual components are the distance tolerance in the housing Δj _a , the toothing tolerances Δj _F , the component tolerances Δj _B , the bearing clearances Δj _S and the different thermal expansion of the wheel body and housing

,

als Funktion der Betriebstemperatur dargestellt, wobei beim Summenzeichen die Einzelanteile beider Zahnräder addiert sind. Die Zahnradpaarungen bestehen dabei aus Stahl, weisen identische Grunddaten (Achsabstand, Modul, Zähnezahl) auf und sind in einem Aluminiumgehäuse gelagert. Das obere Zahndickenabmaß A_ste wurde jeweils so gewählt, dass das kleinste Verdrehflankenspiel j_tmin gerade zu Null wird.The influence of these various individual components on the maximum backlash j _tmax is in 3 for two gear pairs with different operating pressure angle

shown as a function of the operating temperature, with the sum of the individual parts of both gears added. The gear pairs are made of steel, have identical basic data (center distance, module, number of teeth) and are mounted in an aluminum housing. The upper tooth thickness dimension A _ste was chosen so that the smallest _torsional backlash j _tmin just becomes zero.

des Radkörper aus Stahl und des Aluminiumgehäuses.Obviously, the greatest influence on the maximum torsional backlash j _tmax has in the case of the temperature _{limit values} shown in the timing drive of an internal combustion engine of -40 ° C to + 140 ° C in both cases 3 the different thermal expansion

of the steel wheel center and the aluminum housing.

ist das maximale Verdrehflankenspiel j_tmax verringerbar. So ergibt sich für einen Betriebseingriffswinkel

= 10° ein maximales Verdrehflankenspiel j_tmax, das nur etwa halb so groß ist wie das maximale Verdrehflankenspiel j_tmax für einen Betriebseingriffswinkel

= 20°, vgl. den oberen bzw. unteren Teil der 3. Bei einer unter Normalbedingungen auftretenden Temperatur im Steuerbereich eines Motors von etwa 90°C bis etwa 100°C ist das Verdrehflankenspiel j_tmax bei

= 10° damit kaum größer als das Verdrehflankenspiel j_tmax * bei

= 20° ohne thermischen Dehnungseinfluß.By designing a small operating pressure angle

the maximum torsional backlash j _{tmax can be} reduced. This results in an operating pressure angle

= 10 ° a maximum torsional backlash j _tmax , which is only about half as large as the maximum torsional backlash j _tmax for an operating pressure _angle

= 20 °, cf. the upper or lower part of the 3 , At a temperature in the control range of an engine that occurs under normal conditions of approximately 90 ° C. to approximately 100 ° C., the torsional backlash j _{tmax is} at

= 10 ° thus hardly larger than the torsional backlash j _tmax * at

= 20 ° without the influence of thermal expansion.

ist daher kleiner als 14°, vorzugsweise kleiner als 11° und gegebenenfalls kleiner als 8°.The operating pressure angle

is therefore less than 14 °, preferably less than 11 ° and possibly less than 8 °.

= 20°, 15° bzw. 10° sind durch Abwälzsimulation eines Verzahnwerkzeuges mit verschiedenen Profilwinkeln erzeugt und basieren auf einer Hochverzahnung mit einer identischen Profilüberdeckung von ε_α = 2,0 und identischen Grunddaten.In the 4a . 4b and 4c shown tooth profiles of wheel pairs of different operating pressure angles

= 20 °, 15 ° or 10 ° are generated by a gear hobbing simulation with different profile angles and are based on a high toothing with an identical profile coverage of ε _α = 2.0 and identical basic data.

rücken der Grundkreis, also der Beginn des evolventischen Teils, und der Wälzkreis näher zusammen. Dadurch nimmt die nutzbare Höhe des Zahnprofils zwischen dem Fußnutzkreisdurchmesser d_Nf und dem Kopfkreisdurchmesser ab. Um die nutzbare Flankenhöhe nicht durch Hinterschneidung im Fußbereich weiter zu verringern und die Profilüberdeckung konstant zu halten, kann bei kleinen Betriebseingriffswinkeln auf eine Fertigung ohne Protuberanzwerkzeuge übergegangen werden, vgl. 4c, beispielsweise durch Schaben/Nitrieren oder ein komplettes Schleifen des Zahnprofils einschließlich des Zahngrunds. In letzterem Fall muss die verminderte Zahnfußtragfähigkeit, i. A. die Tragfähigkeit des ungehärteten Grundwerkstoffs, infolge der abgetragenen Härteschicht berücksichtigt werden.With decreasing operating pressure angle

move the base circle, i.e. the beginning of the involute part, and the pitch circle closer together. As a result, the usable height of the tooth profile between the root effective circle diameter d _Nf and the tip circle diameter decreases. In order not to further reduce the usable flank height by undercutting in the foot area and to keep the profile overlap constant, it is possible to switch to production without protuberance tools at small operating pressure angles, cf. 4c , for example by scraping / nitriding or a complete grinding of the tooth profile including the tooth base. In the latter case, the reduced tooth load bearing capacity, i. A. The load-bearing capacity of the unhardened base material, due to the removed hardening layer, must be taken into account.

ist daher vorzugsweise größer als 3° und gegebenenfalls größer als 5°.The operating pressure angle

is therefore preferably greater than 3 ° and possibly greater than 5 °.

Claims (8)

Gear transmission, in which two toothed wheel bodies intermeshing with a predetermined backlash ( 1 . 4 ) are subjected to a change in position transversely to their axis of rotation and a dynamic alternating stress during operation, which change the backlash, characterized in that the operating pressure angle (

) the gearing ( 2 . 3 ) is less than 14 ° to minimize the influence of the position change on the backlash. Gear transmission according to claim 1, characterized in that the operating pressure angle (

) is less than 11 °. Gear transmission according to claim 1, characterized in that the operating pressure angle (

) is less than 8 ° or less than 5 °. Gear transmission according to one of claims 1 to 3, characterized in that the operating pressure angle (

) is greater than 3 °. Gear transmission according to one of claims 1 to 3, characterized in that the operating pressure angle (

) is greater than 5 °. Gear transmission according to one of claims 1 to 5, characterized in that a housing is provided in which the wheel body ( 1 . 4 ) are stored, and the housing and the wheel center ( 1 . 4 ) have different coefficients of thermal expansion. Gear transmission according to one of claims 1 to 6, characterized in that it Is part of an internal combustion engine. Use of a gear transmission according to egg nem of claims 1 to 7 in steering wheel drives in internal combustion engines.