A sound generating mechanism 60 includes a sounding member 61, a
retaining member 62, a sounding pin 64, and a coil spring 65.
The sounding member 61 includes a disk portion 61a formed
into a ring shape, a plurality of sounding concavities 61b formed
circumferentially apart on the disk portion 61a, and engagement portions
61c integrally formed with the disk portion 61a. The
retaining member 62 prevents the sounding member 61 from falling
off. The sounding pin 64 is mounted in the knob member 56 at a position
opposite at least one of the sounding concavities 61b so as to be
movable toward and away from the sounding concavities 61b. The coil
spring 65 urges the sounding pin 64 toward the sounding concavities
61b. The sounding pin 64 is unlikely to fall off when the
knob member 56 is attached to or removed from the knob mounting portion
52.