Balanced rotor disc, and balancing method

1. A rotor disc ( 1 ) for a turbomachine, comprising a radial flange ( 2 ) that has a plurality of fastening holes ( 3 ), and a plurality of scallops ( 4 ) forming notches in the flange ( 2 ), and being separated by inter-scallop flange portions ( 7 ), the flange comprising around its circumference in an alternating arrangement:

a single fastening hole ( 3 ) and an inter-scallop flange portion ( 7 ) arranged in the radial extension of the fastening hole ( 3 ), and

a single scallop ( 4 ),

wherein

one or more of the scallops ( 4 7 , 4 8 , 4 9 ; 4 2 , 4 5 - 4 7 , 4 8 - 4 11 , 4 14 ) has a volume greater than the volume of each of the other scallops ( 4 1 - 4 6 , 4 10 - 4 14 ; 4 1 , 4 3 , 4 4 , 4 12 , 4 13 ), and

one or more of the inter-scallop flange portions ( 7 3 ) has a volume less than the volume of each of the other inter-scallop flange portions ( 7 1 , 7 2 , 7 4 ),

in order to balance said disc ( 1 ).

2. The disc ( 1 ) according to claim 1 , wherein:

the scallops ( 4 ) have an apex ( 21 ) on the radial axis, and

all the apexes ( 21 ) of the scallops ( 4 ) are positioned in such a way as to belong to one and the same circle.

3. The disc ( 1 ) according to claim 1 , wherein:

the scallops having a volume greater than the volume of the other scallops are not adjacent to each other, and/or

the inter-scallop flange portions having a volume less than the volume of the other inter-scallop flange portions are not adjacent to each other.

4. The disc according to claim 1 , wherein the flange ( 2 ) extends toward the outside of the disc ( 1 ).

5. A turbomachine comprising a rotor, at least one disc ( 1 ) of which is in accordance with claim 1 .

6. A method for balancing a turbomachine rotor disc ( 1 ) comprising a radial flange ( 2 ) that has a plurality of fastening holes ( 3 ), and a plurality of scallops ( 4 ) forming notches in the flange ( 2 ), and being separated by inter-scallop flange portions ( 7 ), characterized in that the flange alternatively has, in its circumferential direction:

a single fastening hole ( 3 ) and an inter-scallop flange portion ( 7 ) arranged in the radial extension of the fastening hole ( 3 ), and

a single scallop ( 4 ),

the method comprising the steps:

measuring (E 1 ) the imbalance of the disc ( 1 );

machining (E 3 )

one or more scallops ( 4 7 , 4 8 , 4 9 ; 4 2 , 4 5 - 4 7 , 4 8 - 4 11 , 4 14 ), in order for the latter ( 4 1 , 4 2 , 4 3 ) to have a volume greater than the volume of each of the other scallops ( 4 1 - 4 6 , 4 10 - 4 14 ; 4 1 , 4 3 , 4 4 , 4 12 , 4 13 ), and

one or more inter-scallop flange portions ( 7 3 ) in order for the latter to have a volume less than each of the other inter-scallop flange portions ( 7 1 , 7 2 , 7 4 ),

in such a way as to balance the disc ( 1 ) with respect to the measured imbalance.

7. The method according to claim 6 , comprising a step (E 2 ) selecting the scallops and/or inter-scallop flange portions to be machined as a function of the amplitude and/or angular position of the measured imbalance.

8. The method according to claim 6 , wherein:

prior to the machining step, the scallops ( 4 ) have an apex ( 21 ) on the radial axis of the disc, and

the step of machining the scallops ( 4 ) does not alter the position of said apexes on a radial axis of the disc ( 1 ).