DIN 3961-1978圆柱齿轮啮合公差基础(3)

t). I f there deviations are Fil and Fiz a measured value of

F~=

V F+~F;fi=

deviations over discretionary pitch-spans. Their values are found from the formula or the diagram in DIN 3962 Part 3 and they require separate agreement. A pitch-span measurement can be evaluated by plotting the positive and negative tolerance values on tracing paper versus the number of teeth z. The scales of Fp and z must agree with those of the test chart, and in this the z axis must be a t right angles t o the Fpkaxis. I f the zero point of the diagram i s moved along the pitch-spancurve of the test chart, keeping the z axes parallel, the pitchspan curve must lie a t all times within the two tolerance . curves, Fig. 3 Another method is t o determine the pitch-spandeviation Fpk and the associated span at the point of maximum increase in the test chart, Fig. 3 right. This measured value of Fp is then compared with the value permitted according to the diagram in DIN 3962 Part 3 for the same span.

will be expected according to the quadratic error propagation law. I n a working test of two gears (master gears) having approximately the same gear tooth quality, therefore, only 1.4 times the tolerance value of this quality can be accepted. Hence for these applications the standardized quoting of permissible working deviations is s t i l l meaningful for fine gear tooth qualities. A binding quality test according to this method i s however only possible if the uncertainty of measurement can be kept small enough, cf. VDINDE 2608.

6.5 Individual pitch deviations and pitch errorsIf mavericks occur in individual pitch measurements, it i s permissiblet o make measurements a t different points on the flanks and to derive averages for each pitch. The resulting series of measurements i s then used as the basis for assessing the individual pitch deviation and pitch error. No further mavericks are permissible in this. When making pitch measurementswith two spherical tracers it is important to ensure that the second tracer contacts the flanks each time a t exactly the same spot as the first tracer in the preceding pitch. Apart from the pitch deviation tolerances laid down in DIN 3962 Part 1 and Part 3 there are also other characteristics for assessing pitch, e. g. the arithmetic mean or root mean square values of the pitch deviations. They may form the subject of separate agreements;see also VDI/ VDE 2605.

6.4 Pitch-spandeviations over discretionary pitch-spans In general the tolerancing and testing of pitch-spansover 45" and 180' of the gear circumference according t o the values F p s/8 and Fp in DIN 3962 Part 1 i s perfectly adequate. ln some cases, however, and particularly where high-speed gears are involved, it may be necessary in certain circumstances to further restrict the pitch-span

Figure 3. Evaluation of pitch-spanmeasurement

DIN 3961-1978圆柱齿轮啮合公差;基础

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DIN 3961-1978圆柱齿轮啮合公差;基础

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DIN 3961-1978圆柱齿轮啮合公差;基础

Page 12 DIN 3961Gear tooth quality 7 (AGMA gear tooth quality 1 1) Gear#oothquality 9 (AGMA gear tooth quality 9)

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