try this as an exempl:

this code will be in the .py file in a certain class named equipement:

'centre_id':fields.many2one('cvt.centre','_Centre',select=True,required=True),

and here is declaration of the ralated field that I want to show which is placed in a class named centre in the same file:

'properties1':fields.one2many('cvt.equipement','centre_id','_Equipement'),
so the xml file to specify the tree view will be:
<record model="ir.ui.view" id="centre_tree">
                <field name="name">centre.tree</field>
                <field name="model">cvt.centre</field>
                <field name="type">tree</field>
                <field name="arch" type="xml">
                    <tree string="tree">
                        <field name='name'/>
                         ...                          
                        <field name='properties1'/>							
                    </tree>
                </field>
            </record>
 so this will show a new field named _Equipement in center tree view and 
hope this helps you