export excel file maatwebsite laravel

I'm blocking to export an excel file from a table on laravel here's my controller :

    <?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use DB;
use Excel;

class ExportExcelController extends Controller
{
  function Export()
  {
    $customer_data = DB::table('qualys')->get();
    return view('export_excel')->with('customer_data', $customer_data);
  }
  function excel()
  {
    $customer_data = DB::table('qualys')->get();
    $customer_array[] = array('ip','qid');
    // dd($customer_data);
    foreach($customer_data as $customer)
    {
      // dd($customer);
       $customer_array[] = array(
                 'ip' => $customer->qid,
                 'qid' => $customer->ip
      );
    }
    Excel::download('customer_data.xlsx', 'customer_data.xls');

    // Excel::download('customer data', function($excel) use ($customer_array) {
    //      $excel->setTitle('customer Data');
    //      $excel->sheet('Customer Data', function($sheet) use ($customer_array)
    //      {
    //        $sheet->fromArray($customer_array, null, 'A1', false, false);
    //      });
    // })->download('xls', 'test');
  }
}

I'm blocked at line 29 level, I can't get the file back, here's the following error:

Argument 2 passed to Maatwebsite\Excel\Excel::download() must be of the type string, object given, called in /var/www/html/qualys/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php on line 223

I have tested several "code" but nothing works:( can you help me plz? cordially.

via Chebli Mohamed