请问一个jquery 实现input type="button"的背景图片变换

<input type="button" id="t1p1z11" class="imgbutton" value="&nbsp;" onclick="aa()">

 $(document).ready(function() {                     $("#t1p1z11").toggle(function() {                         $("#t1p1z11").css("background-image", "url(1.jpg)");                     }, function() {                         $("#t1p1z11").css("background-image", "url(2.jpg)");                     });                 });