Laravel Eloquent查询建设

I have four tables and I am giving my table structure here

1. user_work['id', 'user_id', 'work_id']
2. work_sectors['id', 'name', 'status']
3. works['id', 'work_sector_id', 'work_type_id', 'work_duration_id', 'name']
4. users['id', ...]

And My Models are

class User extends Eloquent implements UserInterface, RemindableInterface 
{
  use UserTrait, RemindableTrait;
  protected $table = 'users';
  public function work()
  {
       return $this->belongsToMany('Work', 'user_work');
  }
}

class Work extends \Eloquent {
protected $fillable = [];
protected $table_name = 'works';
public $timestamps = false;

public function user()
{
    return $this->belongsToMany('User', 'user_work');
}

public function sector()
{
    return $this->belongsTo('WorkSector', 'work_sector_id');
}
}

In my controller I have written this code

$user = User::with('language')->with('work')->find($userId);

Here I need name of work_sector table but probably I have written wrong code to get the sector name.

So please help me to write a proper function in this eloquent method in laravel 4.2.