Form request not working for controllers within subfolder of Controller folder - laravel-5

Question

My folder structure for controllers is:
and I use following route code to access those controllers.
here I have allocated sub-folders inside Controller folder and updated namespaces as per needed on files and routes accordingly, this works perfectly, however when I use request file for validating form. It gives error:
Argument 1 passed to App\Http\Controllers\site\usersController::store()
must be an instance of Illuminate\Http\Request, string given
but when I move all controllers file to Controller folder and don't use sub-folder,form request validation works.My usersController and UserRegReq request files are:
usersController.php
<?php
namespace App\Http\Controllers\zcms;
use Illuminate\Http\Request;
use App\Services\FieldService;
use App\Services\UserService;
use App\Http\Requests;
use App\Http\Requests\UserRegReq;
use App\Http\Controllers\Controller;
class usersController extends Controller {
public function __construct(FieldService $field, UserService $user)
{
$this->field = $field;
$this->user = $user;
}
/**
* Display a listing of the resource.
*
* #return Response
*/
public function index()
{
//
}
/**
* Display a listing of the resource.
*
* #return Response
*/
public function throwLogin()
{
return view('zcms.pages.login');
}
/**
* Show the form for creating a new resource.
*
* #return Response
*/
public function create()
{
$field = $this->field->fieldList();
return view('zcms.users.addnew', compact('field'));
}
/**
* Store a newly created resource in storage.
*
* #param Request $request
* #return Response
*/
public function store(UserRegReq $request)
{
return "hello";
}
/**
* Display the specified resource.
*
* #param int $id
* #return Response
*/
public function show($id)
{
//
}
/**
* Show the form for editing the specified resource.
*
* #param int $id
* #return Response
*/
public function edit($id)
{
//
}
/**
* Update the specified resource in storage.
*
* #param Request $request
* #param int $id
* #return Response
*/
public function update(Request $request, $id)
{
//
}
/**
* Remove the specified resource from storage.
*
* #param int $id
* #return Response
*/
public function destroy($id)
{
//
}
}
UserRegReq.php
<?php
namespace App\Http\Requests;
use App\Http\Requests\Request;
class UserRegReq extends Request {
/**
* Determine if the user is authorized to make this request.
*
* #return bool
*/
public function authorize()
{
return true;
}
/**
* Get the validation rules that apply to the request.
*
* #return array
*/
public function rules()
{
return [
'field_id' => 'required',
'name' => 'required',
'username' => 'required',
'password' => 'required'
];
}
// public function messages(){
// return [
// 'field_id.required'=>'The related Field of your Job is required',
// ];
// }
}
What should I do beside updating namespace in routes and controller file to make everything work?