$this->db->insert add quotes

[eluser]Unknown[/eluser]
Hello,

i try a model in code igniter in connexion with an oracle database.

In my model is:

Code:

function insert_entry()
     {
         $this->firstname   = 'Jojo';
         $this->lastname = 'Jaja';

        $this->db->insert('ci_user', $this);
     }

and here is the result in my page:

Code:

A Database Error Occurred

Error Number:

INSERT INTO "ci_user" ("firstname", "lastname") VALUES ('Jojo', 'Jaja')

can you help me and tell me why ci_user, firstname and lastname words are quoted ?

Thanks for your help