在codeigniter hmvc中加载模型时出错

I load a model in a controller. But I have this error:

Message: Undefined property: Captcha::$captcha_model

And also this message:

Fatal error: Call to a member function captcha_insert() on a non-object in C:\xampp\htdocs\ci-framework\application\modules\captcha\controllers\captcha.php on line 31

Everything seems true!

Controller:

$time = $captcha['time'];
$ip_address = $this->input->ip_address();
$word = $captcha['word'];
$this->load->model('captcha/captcha_model');
$value = $this->captcha_model->captcha_insert($time, $ip_address, $word);

model:

class Captcha_model extends CI_model {


 public function captcha_insert($time, $ip_address, $word){

    $query = $this->db->query("insert into captcha
                                (time, ip_address, word)
                                values(?, ?, ?)",
                                array($time, $ip_address, $word));
    if ($query)
        return true;
 }


}

What's wrong? Thank you very much :)

I searched more and found the answer :)

Not only in module/controller , But also in base controller I have to extend MX not CI. Thank you guys :)