Mechanical timepiece movement with a lever escapement

A mechanical timepiece movement, comprising:

• a balance provided with a pivot shaft;
• an escapement associated with said balance, said escapement comprising a pallet-lever provided with a fork;
• an impulse pin integral with the balance and cooperating with the fork to allow the latter to provide the balance with impulses maintaining the oscillation thereof by a drive force applied to an escape wheel, which is coupled to the pallet-lever;
• and
• two banking elements preventing rotation of the pallet-lever, which define two locking positions of the pallet-lever and between said two locking positions an angular distance for the pallet-lever, said pallet-lever being arranged to move alternately into abutment with the two banking elements in locking periods occurring between said impulses provided to the balance;
• wherein the pallet-lever carries at least one permanent magnet which has an axis of magnetisation oriented substantially tangentially to a circular axis of displacement of said at least one permanent magnet, when the pallet-lever is subjected to said movements of said movements of rotation;
• wherein the timepiece movement comprises a first element of high magnetic permeability and a second element of high magnetic permeability respectively arranged on either side of said at least one permanent magnet so as to be substantially aligned on the circular axis of displacement, the first element of high magnetic permeability and the second element of high magnetic permeability and the two banking elements having substantially the same plane of symmetry;
• wherein the timepiece movement further includes a second permanent magnet integral with the first element of high magnetic permeability and a third permanent magnet integral with the second element of high magnetic permeability, the second permanent magnet being arranged further away from said at least one permanent magnet than the first element of high magnetic permeability, and the third permanent magnet being arranged further away from said at least one permanent magnet than the second element of high magnetic permeability;
• wherein said at least one permanent magnet and a first assembly formed of the second permanent magnet and the first element of high magnetic permeability are arranged to generate, between said at least one permanent magnet and said first assembly, a force of magnetic attraction on a first section of said angular distance and a force of magnetic repulsion on a second section of said angular distance, the second section corresponding to a distance of separation between said at least one permanent magnet and said first assembly that is greater than the distance of separation corresponding to the first section, and
• wherein said at least one permanent magnet and a second assembly formed of the third permanent magnet and the second element of high magnetic permeability are arranged to generate, between said at least one permanent magnet and said second assembly, a force of magnetic attraction on a third section of said angular distance and a force of magnetic repulsion on a fourth section of said angular distance, the fourth section corresponding to a distance of separation between said at least one permanent magnet and said second assembly that is greater than the distance of separation corresponding to the third section.