Key structure and electronic apparatus

1. A key structure in an electronic apparatus case comprising:

a top portion that is exposed through a surface of the case;

a shaft portion having a first portion which has a first width and is in contact with an inner surface of the top portion and a second portion which has a second width smaller than the first width and extends from the first portion to a switch and including an elastomer; and

a stopper portion that projects from a periphery of the top portion and that engages with the shaft portion so as to be in contact with an inner surface of the electronic apparatus case in a state where the elastomer is contracted.

2. The key structure according to claim 1 , wherein the top portion is made of resin harder than elastomer.

3. The key structure according to claim 1 , wherein the shaft portion includes a water stop portion which extends perpendicular from the shaft portion so as to contact a tubular portion in a water tight manner.

4. The key structure according to claim 3 , wherein the shaft portion includes a flange portion that extends from the water stop portion and projects in the direction perpendicular to the direction in which the shaft portion extends.

5. The key structure according to claim 1 , wherein a core material harder than elastomer is included inside the shaft portion.

6. The key structure according to claim 1 , wherein a core material harder than elastomer extends inside the shaft portion from the top portion.

7. The key structure according to claim 4 , wherein drag against an advance of the shaft portion is applied to the key structure by contact between the flange portion and the case.

8. The key structure according to claim 1 , wherein the top portion is provided so as to cover the first portion.

9. An electronic apparatus having a key structure comprising:

a case encasing a circuit board having a switch thereon;

the case includes an internal tubular portion with a through hole formed therein;

the key structure includes:

a top portion that is exposed through a surface of the case,

a shaft portion having a first portion which has a first width and is in contact with an inner surface of the top portion and a second portion which has a second width smaller than the first width and extends from the first portion to a switch through the tubular portion, including an elastomer and contacting the switch, and

a stopper portion that projects from a periphery of the top portion and that engages with the shaft portion so as to be in contact with an inner surface of the electronic apparatus case in a state where the elastomer is contracted.

10. The electronic apparatus according to claim 9 , wherein the shaft portion extends through the tubular portion so that a small diameter portion of the shaft portion contacts a movable axis of the switch;

the shaft portion includes a water stop portion which extends perpendicular from the shaft portion so as to contact the tubular portion in a water tight manner.

11. The electronic apparatus according to claim 10 , further comprising:

a flange portion that extends from the water stop portion toward the top portion and reaches outside of the tubular portion.

12. The electronic apparatus according to claim 9 , further comprising:

a projecting portion that projects from an outer periphery of the top portion in the case in a direction in which the shaft portion extends.

13. The electronic apparatus according to claim 11 , wherein the flange portion is configured so as to create drag on the shaft portion in a direction toward the switch.

14. The electronic apparatus according to claim 12 , wherein the projecting portion abuts the tubular portion and deforms by pressure on the top portion so as to cause resilience to the top portion.

15. The electronic apparatus according to claim 9 , wherein the top portion is provided so as to cover the first portion.