jQuery('#nome_r').keyup(function () {
        this.value = this.value.replace(/[^A-Za-záàâãéèêíïóôõöúçñÁÀÂÃÉÈÍÏÓÔÕÖÚÇÑ ]/g,'');
    });

<label>Nome completo</label>
<input type="text" class="form-control form-control-danger" id="nome_r" placeholder="Seu nome">