rails devise, no route matches logout

Though there're lots of similar questions, i've searched for it for hours but still can not fix it.

Env rails 3.0.9 ruby 1.9.2 devise 1.4.2

I changed the default login url using:

 5   resources :users
 6   devise_for :users, :path => "", :path_names => { :sign_in => 'login', :sign_out  
     => 'logout', :password => 'secret', :confirmation => 'verification', :unlock =>
     'unblock', :registration => 'register', :sign_up => 'cmon_let_me_in' }

And the http://localhost:3000/login works fine for me But I include

 = link_to 'sign_out', destroy_user_session_path, :method => :delete

in my application.haml, after i click it, it says that no route matchs "/logout" Why? Please help me.