Wood-type golf club head

1. A hollow wood-type golf club head comprising a face portion having a face for hitting a golf ball, a sole portion constituting the bottom of the club head, and a junction interconnecting the face portion and the sole portion and including at least one thick wall portion, said at least one thick wall portion having a thickness larger than a thickness at a lower edge of the face portion and having a length L of 20 mm or more wherein the length L is a total of lengths in a toe-heel direction of said at least one thick wall portion disposed in the club head, wherein a ratio L/La of the length L of said at least one thick wall portion to a length La of said junction is from 0.10 to 0.90.

2. The golf club head of claim 1 , wherein a single thick wall portion is disposed at the junction.

3. The golf club head of claim 1 , wherein in a standard state that the club head is placed on a horizontal plane at prescribed lie and loft angles, said at least one thick wall portion extends across a vertical plane including the head's center of gravity and the sweet spot.

4. The golf club head of claim 1 , which has a volume of 380 to 500 cm 3 .

5. The golf club head of claim 1 , which has a weight of 180 to 220 g.

6. The golf club head of claim 1 , wherein said at least one thick wall portion has such a sectional shape that outer and inner surfaces of said junction are formed into arc surfaces convex toward outward of the club head, and a ratio Ri/Ro of a radius of curvature Ri of the inner surface to a radius of curvature Ro of the outer surface is from 1.2 to 20.

7. The golf club head of claim 1 , wherein said at least one thick wall portion has such a sectional shape that an outer surface of said junction is an arc surface convex toward outward of the club head, and an inner surface of said junction is an inclined plane which extends from the sole portion toward a crown portion of the club head and is inclined toward the face.

8. The golf club head of claim 1 , wherein said at least one thick wall portion has such a sectional shape that an outer surface of said junction is an arc surface convex toward outward of the club head, and an inner surface of said junction is an arc surface convex toward inward of the club head.

9. The golf club head of claim 1 , wherein said at least one thick wall portion has a thickness t 2 of 2.0 to 8.0 mm.

10. The golf club head of claim 1 , wherein a thickness t 1 at the lower edge of the face portion is from 1.5 to 4.5 mm.

11. The golf club head of claim 1 , wherein a thickness t 3 at a front edge of the sole portion is from 1.5 to 4.0 mm.

12. The golf club head of claim 1 , wherein a ratio t 3 /t 2 of a thickness t 3 at a front edge of said sole portion to a thickness t 2 of said at least one thick wall portion is from 0.10 to 0.90.

13. The golf club head of claim 1 , wherein a plurality of thick wall portions are disposed at intervals at said junction, and a length Li of each of said thick wall portions is at least 0.10 times a whole thickness La of said junction.

14. The golf club head of claim 13 , wherein the length Li of each of said thick wall portions in a toe-heel direction of the club head is at least 10 mm.

15. A hollow wood-type golf club head comprising a face portion having a face for hitting a golf ball, a sole portion constituting the bottom of the club head, and a junction interconnecting the face portion and the sole portion and including at least one thick wall portion, said at least one thick wall portion having a thickness larger than a thickness at a lower edge of the face portion and having a length L of 20 mm or more wherein the length L is a total of lengths in a toe-heel direction of said at least one thick wall portion disposed in the club head, wherein a plurality of thick wall portions are disposed at intervals at the junction.

16. A hollow wood-type golf club head comprising a face portion having a face for hitting a golf ball, a sole portion constituting the bottom of the club head, and a junction interconnecting the face portion and the sole portion and including at least one thick wall portion, said at least one thick wall portion having a thickness larger than a thickness at a lower edge of the face portion and having a length L of 20 mm or more wherein the length L is a total of lengths in a toe-heel direction of said at least one thick wall portion disposed in the club head, wherein thickness t 2 of said at least one thick wall portion is larger than thickness t 1 at the lower edge of the face portion by at least 0.5 mm.

17. The golf club head of claim 16 , wherein a ratio t 1 /t 2 of the thickness t 1 at the lower edge of the face portion to the thickness t 2 of said at least one thick wall portion is from 0.30 to 0.95.