无法使用Codeigniter将值插入数据库

尝试使用codeigniter将表单值插入数据库中，但没有发生任何变化。我的表单是comment_form.php就像，

<?php echo validation_errors(); ?>
<?php echo form_open('news/comment_form'); ?>

Name<input type="text" name="comment_name"></input><br />
Email<input type="text" name="comment_email"></input><br />
Comment<input type="text" name="comment_body"></input><br />
<input type="submit" name="submit" value="Comment it" ></input>

</form>

这是我的控制器comments.php

class Comments extends CI_Controller
{

    public function __construct()
    {
        parent::__construct();
        $this->load->model('comment_model');
    }

    public function create_comment()
    {
        $this->load->helper('form');
        $this->load->library('form_validation');


        //$data['title'] = 'Create a news item';

        $this->form_validation->set_rules('comment_name', 'comment_name', 'required');
        $this->form_validation->set_rules('comment_email', 'comment_email', 'required');
        $this->form_validation->set_rules('comment_body', 'comment_body', 'required');

        if ($this->form_validation->run() === FALSE) {
            $this->load->view('templates/header', $data);
            $this->load->view('news/comment_form');
            $this->load->view('templates/footer');
        } else {
            $this->news_model->set_comment();
            $this->load->view('news/success');
        }
    }
}

这是我的模型comment_model.php

class Comment_model extends CI_Model
{

    public function __construct()
    {
        $this->load->database();
    }


    public function set_comment()
    {
        //$this->load->helper('url');

        //$slug = url_title($this->input->post('title'), 'dash', TRUE);

        $datac = array(
            'comment_name' => $this->input->post('comment_name'),
            'comment_email' => $this->input->post('comment_email'),
            'comment_body' => $this->input->post('comment_body')
        );

        return $this->db->insert('comments', $datac);
    }
}

问题是，每当我提交表单时，它都不会返回任何内容，就像什么都没有发生。请帮助。