Page 293 - Gear Technology Solutions

The Gleason V-H-Check moves the contact pattern from a center position to a
position between center and heel and then to a position between center and
toe (see Figure 4).

The difference between the axes positions in heel and toe position are the total
V-H-displacement numbers. Bevel gear transmission housing designers use
these total V-H-numbers in order to optimize the stiffness and the deflection
characteristic of the transmission housing. As soon as a housing concept ex-
ists, finite element calculations of the gearbox deflection are used to calculate
predicted shaft positioning deviations, which are then used as input to the con-
tact analysis program in order to verify which influence the calculated deflec-
tions have on the position of the tooth contact. Depending on the resulting
tooth contact, tooth surface optimization has to be conducted in order to adjust
the deflection characteristic to the transmission housing. This loop between
transmission housing design and bevel gear optimization has to be repeated
multiple times to assure a displacement characteristic of the bevel gearset
which offsets the housing deflections.
.

Figure 4: Gleason V-H-Check

The attempt to provide shaft deflection tolerances using the V-H-Check deflec-
tion numbers showed severe shortcomings, as the V-H-Check fails to identify
the changing backlash. In cases of load affected deflections the increase of
backlash is acceptable and does not present any obstacles. An exception is
the case of coast side operation, where the backlash reduces, and severe
flank surface damage can occur.

However, the general tolerances for the positioning of bevel and hypoid gear
shafts has to be based on both, the contact movement as well as the allowable
reduction or increase of the backlash as a result of the shaft miss-positioning.

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