如何在ajax按钮单击上运行pdf功能

Question

我正在尝试在ajax按钮单击上生成pdf，但结果未显示在pdf中。

ajax

 $('#Expnpdf').on('click', function() { 
        var data2_value = $('#expenses').val(); 
            $.ajax({
                   type: 'post',
                   url: 'expense_report_pdf',
                   data: {type:data2_value},
                   success: function (data) {
                               if (data.length > 0) {
                               var url = data['expense_report_pdf'];
                                window.location = url;
                                }
                            }
              });

 });

功能

public function expense_report_pdf()
   {
    $data=$this->Report_model->expense_report();    
    $this->load->library('Pdf');
    $pdf = new TCPDF('L', 'mm', array(400,400), true, 'UTF-8', false);
    $pdf->SetTitle('Enquiry Report');
    $pdf->SetHeaderMargin(20);
    $pdf->SetTopMargin(10);
    $pdf->setFooterMargin(10);
    $pdf->SetAutoPageBreak(true);
    $pdf->SetAuthor('Author');
    $pdf->SetDisplayMode('real', 'default');
    $pdf->AddPage();
    $html = $this->load->view('Admin/exp_pdf',$data,true);
    $pdf->writeHTML($html, true, false, true, false, '');
    ob_end_clean();     
    $pdf->Output();
 }

success的结果为true，但没有生成pdf，如何解决此问题？请帮帮我！