EXCLUSIVE

Usher's ex-wife has just filed legal docs asking for an emergency hearing later this week ... to wrestle child custody away from him, on grounds he's creating a dangerous environment ... TMZ has learned.

Tameka Raymond filed the docs in Fulton County, Georgia, claiming Usher is abdicating his parental responsibilities by letting other people care for their 2 kids -- people who she claims are not on the ball.

We know Tameka has specific beef with the Usher's aunt -- who was watching 5-year-old Usher Raymond V when his arm got stuck in the pool drain on Monday. Tameka has complained about the aunt in the past -- alleging she once let a stalker in the house where Usher and the kids were staying. Tameka also says the aunt is too physical in disciplining the kids.