PROBLEMA COM AJAX

<script>
            $(''#btn_apont'').click(function () {
                var dataini = $(''#dataini'').val();
                var datafim = $(''#datafim'').val();
                $.ajax({
                    type: ''POST'',
                    contentType: "application/json; charset=utf-8",
                    url: ''rel_apontamentos.php'',
                    async:false,
                    data:{''data_ini'':dataini, ''data_fim'':datafim }
                    ,
                    erro: function () {
                        alert(''erro'');
                    },
                    success: function (data) {
                        $("#carrega_ap").html(data);
                    }

                });
            });
    </script>