PHP mysql query

I have the following problem I can not make a query to mysql from the html form, the error is in the mysql query

  

Unable to execute query.You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 1

Will it be that the values in the Patent field are alphanumeric?

<?php
    if(isset($_POST['btnConsulta'])) {
      $conn = mysqli_connect("localhost", "root", "", "movedb");
      $patente= $_POST['patente'];
      $query = "SELECT * from tablaunion1 where Patente=$patente";
      $resultados= mysqli_query($conn, $query) or die ('Unable to execute query.'. mysqli_error($conn));
    }
?>

This is the code html

<!-- COmienzo de formulario -->

<section class="content">
  <div class="container-fluid">        
    <div class="row clearfix">
       <div class="col-lg-12">
        <div class="card">
          <div class="header">
           <h2>Consulta x móviles</h2>

          </div>
        <div class="body">

        <form  method="POST" action="consultaxmovil.php" name="frm">
          <div class="row clearfix">
              <div class="col-md-3">
                <div class="form-group-horizontal">
                  <label class="control-label">Patente</label>
                  <input name="patente" id="patente" maxlength="10" type="text" class="form-control" onKeyup="this.value=this.value.toUpperCase();">
                </div>
              </div>

              <div class="col-md-3">
                <h2></h2>
                <button type="button" class="btn bg-blue btn-lg-l-15 waves-effect" data-toggle="modal" data-target="#exampleModal">
                <i class="material-icons">Buscar</i></button>
              </div>

              <div class="col-md-6">
                <div class="form-group-horizontal">
                  <label class="control-label">Area</label>
                  <input  type="text"  class="form-control " placeholder="Area Responsable" name="area" id="area" readonly>
                </div>
              </div>

              <div class="col-md-6">
                <div class="form-horizontal">
                  <label class="control-label">Interno</label>
                  <input  type="text"  class="form-control form-control-danger" placeholder="Interno" name="interno" id="interno" readonly>
                </div>
              </div>

              <div class="col-md-6">
                <div class="form-horizontal">
                  <label class="control-label">Marca</label>
                  <input  type="text" id="Marca" class="form-control form-control-danger" placeholder="Marca movil" name="marca" id="marca" readonly>
                </div>
              </div>

              <div class="col-md-6">
                <div class="form horizontal">
                  <label class="control-label">Fecha desde:</label>
                  <input name= "Fechadesde" type="date" class="form-control"  placeholder="dd/mm/yyyy" title="Por favor ingrese fecha desde">
                </div>
              </div>

              <div class="col-md-6">
                <div class="form horizontal">
                  <label class="control-label">Fecha hasta:</label>
                  <input name= "Fechahasta" type="date"  class="form-control" placeholder="dd/mm/yyyy" title="Por favor ingrese fecha desde" >
                </div>                                            
              </div>


              <div class="card-footer">


                  <div class="col-md-8 col-md-offset-6">
                    <button name="btnConsulta" class="btn btn-primary" type="submit">Consulta</button>
                    &nbsp;&nbsp;&nbsp;<button class="btn btn-default icon-btn" href="#" class="fa fa-fw fa-lg fa-times-circle" type="button">Nuevo</button>
                    <button class="btn btn-primary icon-btn" type="button"><i class="fa fa-fw fa-lg fa-check-circle"></i>Salir </button>&nbsp;&nbsp;&nbsp;
                  </div>
                </div>