Shunt tube flowpaths extending through swellable packers. As the engine of the car is running, the electrical metal sensor will be activated. The cover member 13 is folded, thereby the light of the display image displayed on a display surface 23a of the display device 23 is reflected on a reflector 25 disposed in the cover member 13 to the optical element 21, passes through the optical element 21, and goes toward the eye point I after being reflected by the combiner 7.