mysql中的timestamps字段不起作用

<code><?php use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateEquip extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('equip', function (Blueprint $table) {
            // $table->increments('id');
            $table->smallInteger('equip_id')->unsigned()->comment('装备id');
            $table->string('eqiup_name')->comment('装备名称');
            $table->string('eqiup_desc')->comment('装备描述');
            $table->timestamps();
            $table->primary('equip_id');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        //
    }
}
</code>