How to create JQuery Class Private Variable

How to create JQuery Class Private Variable

Hi all,
 
I am not a JQuery expert so I am very confused about creating private variable for an object instance.
I want to create a simple jquery plugin, but all instances see the last declared class variables.
 
Can someone tell me the reason and the solution ?
 
Sample code :
 
; ( function ( $ ) {
 
     /* This is a private declaration, isn't it ? */
    var settings = {
        pagesize: 10
    }

 
    /* Constructor */
    $.fn.myPlugin = function (options ) {
       
       /* Call a private method to save the options */
        setVars ( options );
    }
 
    /* Private method to save the options to a PRIVATE variable */
    function setVars(options) {
        settings = $.extend ( {}, options );
    }
 
    /* Alert the page size related to the CURRENT instance */
    $.fn.myPlugin.refresh = function () {
        alert( settings.pagesize );
    }
 
} ) ( jQuery );
 
Calling the plugin :
 
(" #div1").myPlugin ( {
      pagesize : 11
} );
 
$(" #div2").myPlugin ( {
      pagesize : 45
} );

$("#div1").myPlugin.refresh();
$("#div2").myPlugin.refresh();

 
I think the result should be to alert 11 and 45 but only 45 is alerted two times. But why ?
 
Thank you in advance
Tihi