目前的做法是

# encoding : utf-8 -*- 
class TaobaoAppToken < ActiveRecord::Base

    attr_accessible :access_token, :refresh_token, :last_refresh_at, :refresh_token_last_refresh_at 

    def check_or_refresh!
      refresh_token_refresh = Time.now - self.refresh_token_last_refresh_at 
      if refresh_token_refresh > 3600 #1 hours
      base_url = "https://oauth.taobao.com/token?"          
      params = { 
                  client_id: Setting.taobao_app_key,
                  client_secret: Setting.taobao_app_secret, 
                  grant_type: 'refresh_token',
                  refresh_token: self.refresh_token             
                  }.to_params       

      response = HTTParty.post(base_url + params).parsed_response
      if response['access_token'].present?
        self.update_attributes(access_token: response['access_token'], last_refresh_at: Time.now, refresh_token: response['refresh_token'], refresh_token_last_refresh_at: Time.now )
     else 
        Notifier.app_token_errors(self,response).deliver
     end     
      end   
    end 
end

每天会请求 12 次刷新，每次刷新都能获取到新的 acess_token 和 refresh_token, 但是认证一天后还是会提示 refresh_token 过期