Golf club head

1. A golf club head comprising: a face part; a sole part; and a crown part, wherein

the head is hollow;

the head has an inner surface on which a rib (X 1 ) and a rib (X 2 ) are provided, the rib (X 1 ) and the rib (X 2 ) having a height greater than a thickness;

the rib (X 1 ) and the rib (X 2 ) are separated from the face part and separated from the crown part;

extending directions of the rib (X 1 ) and the rib (X 2 ) are inclined with respect to a front-back direction of the head in a projected image obtained by projecting the head setting to the standard condition on a horizontal plane H;

the rib (X 1 ) extends toward a heel side in the direction of a backside of the head, and the rib (X 2 ) extends toward a toe side in the direction of the backside of the head;

the rib (X 1 ) and the rib (X 2 ) have a height change part formed in a face side end part of the ribs, the height change parts having a height gradually lowered as approaching rib end parts;

a ratio [Rh/Rt] of a height Rh of the rib (X 1 ) to a thickness Rt of the rib (X 1 ) is 2 or greater and 20 or less, and a ratio [Rh/Rt] of a height Rh of the rib (X 2 ) to a thickness Rt of the rib (X 2 ) is 2 or greater and 20 or less; and

a rib (Y) having a height equal to or less than a thickness and lower than the maximum height of the rib (X 1 ) and the rib (Y) connects the height change part of the rib (X 1 ) to the height change part of the rib (X 2 ).

2. The golf club head according to claim 1 , wherein

the rib (X 1 ) is located on the heel side of the rib (X 2 ).

3. The golf club head according to claim 1 , wherein the rib (Y) is separated from the face part;

the rib (Y) is separated from the crown part; and

the rib (Y) is separated from a hosel part.

4. The golf club head according to claim 1 , wherein the rib (Y) extends in a curved condition.

5. The golf club head according to claim 4 , wherein the rib (Y) is curved so as to project toward the backside of the head.

6. The golf club head according to claim 1 , wherein

the rib (X 1 ) has a height change part formed in a backside end part of the rib (X 1 ), the height change part having a height gradually lowered as approaching the rib end part; and

the rib (X 2 ) has a height change part formed in a backside end part of the rib (X 2 ), the height change part having a height gradually lowered as approaching the rib end part.

7. The golf club head according to claim 1 , wherein an angle α between an extending direction Dr of the rib (X 1 ) and the rib (X 2 ) and a front-back direction fb of the head is 10 degrees or greater and 80 degrees or less.

8. The golf club head according to claim 1 , wherein a height Rh of the rib (X 1 ) and the rib (X 2 ) is 1 mm or greater and 30 mm or less.

9. The golf club head according to claim 1 , wherein a thickness Rt of the rib (X 1 ) and the rib (X 2 ) is 0.1 mm or greater and 5 mm or less.

10. The golf club head according to claim 1 , wherein a length Lr of the rib (X 1 ) and the rib (X 2 ) is 5 mm or greater and 150 mm or less.

11. The golf club head according to claim 1 , wherein an angle θ 1 between a tangent line Lf in the face side end part of the rib (X 1 ) and the rib (X 2 ) and an inner surface of the head in the end part is 10 degrees or greater and 80 degrees or less.

12. The golf club head according to claim 1 , wherein an angle θ 2 between a tangent line Lb in the backside end part of the rib (X 1 ) and the rib (X 2 ) and an inner surface of the head in the end part is 10 degrees or greater and 80 degrees or less.

13. The golf club head according to claim 1 , wherein a thickness T 1 of a head body at a region of on which the rib (X 1 ) and the rib (X 2 ) are provided is 0.4 mm or greater and 4 mm or less.

14. The golf club head according to claim 1 , wherein a thickness T 2 of a head body at a region on which the rib (Y) is provided is 0.4 mm or greater and 4 mm or less.

15. The golf club head according to claim 1 , wherein a volume of the head is 350 cc or greater and 460 cc or less.

16. The golf club head according to claim 1 , wherein a weight of the head is 180 g or greater and 300 g or less.

17. The golf club head according to claim 4 , wherein the dimension of the height change parts of the rib (X 1 ) and the rib (X 2 ) along the extending direction of the rib (X 1 ) and the rib (X 2 ) is greater than the dimension of the rib (Y) along the extending direction of the rib (X 1 ) and the rib (X 2 ).