Frame structure for saddle-type vehicle

1. A frame structure for a saddle vehicle, comprising:

a hollow main frame extending rearwardly from a head pipe; and

an air cleaner including a filter element disposed in the hollow main frame, said air cleaner being divided into a dirty side and a clean side by the filter element, the hollow main frame having a front opening defined in a front portion thereof for introducing intake air,

wherein the hollow main frame includes an inner wall surface having a first rib extending peripherally and projecting inwardly into a space in the hollow main frame, and a second rib disposed upstream or downstream of the first rib with respect to an intake air flow and projecting inwardly into the space in the hollow main frame,

wherein the filter element has an engaging member extending substantially along the inner wall surface and engageable with the second rib,

wherein the first rib peripherally surrounds the filter element to provide a division wall with the second rib engaging the filter element to support the filter element, and

wherein, as viewed in a sectional side elevation of the hollow main frame, a lower rib wall section of the first rib and a lower wall surface of the inner wall surface which is slanted downwardly toward a projection proximal portion of the lower rib wall section jointly define therebetween a downwardly recessed space disposed upstream of the lower rib wall section of the first rib with respect to the intake air flow.

2. The frame structure for a saddle vehicle, according to claim 1 , wherein a third rib projects inwardly into the space in the hollow main frame and is disposed between the first rib and the second rib in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

3. The frame structure for a saddle vehicle, according to claim 2 , wherein the filter element has a flange in a position overlapping the third rib as viewed along the direction of the intake air flow, the flange having a round end surface on a distal end thereof.

4. The frame structure for a saddle vehicle, according to claim 1 , wherein the hollow main frame has an upper opening defined in an upper portion thereof;

the upper opening is closed by an upper lid; and

the upper lid has a fourth rib disposed on an inner surface thereof and projecting in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

5. The frame structure for a saddle vehicle, according to claim 2 , wherein the hollow main frame has an upper opening defined in an upper portion thereof;

the upper opening is closed by an upper lid; and

the upper lid has a fourth rib disposed on an inner surface thereof and projecting in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

6. The frame structure for a saddle vehicle, according to claim 3 , wherein the hollow main frame has an upper opening defined in an upper portion thereof;

the upper opening is closed by an upper lid; and

the upper lid has a fourth rib disposed on an inner surface thereof and projecting in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

7. The frame structure for a saddle vehicle, according to claim 4 , wherein, as viewed in a sectional side elevation of the hollow main frame, the second rib is disposed downstream of the first rib with respect to the intake air flow and is located within a vertically projected range of the upper opening.

8. The frame structure for a saddle vehicle, according to claim 1 , wherein the hollow main frame has a water drain hole defined therein upstream of the filter element with respect to the intake air flow and positioned downwardly of at least an element filter.

9. The frame structure for a saddle vehicle, according to claim 2 , wherein the hollow main frame has a water drain hole defined therein upstream of the filter element with respect to the intake air flow and positioned downwardly of at least an element filter.

10. The frame structure for a saddle vehicle, according to claim 1 , wherein the hollow main frame is composed of an integral structural component produced by casting.

11. The frame structure for a saddle vehicle, according to claim 2 , wherein the hollow main frame is composed of an integral structural component produced by casting.

12. A frame structure for a saddle vehicle, comprising:

a hollow main frame extending rearwardly from a head pipe;

a front opening defined in a front portion of the hollow main frame for introducing intake air into a space formed in the hollow main frame;

an inner wall surface formed within the hollow main frame, said inner wall surface having a first rib extending peripherally and projecting inwardly into the space in the hollow main frame, and a second rib disposed upstream or downstream of the first rib with respect to an intake air flow and projecting inwardly into the space in the hollow main frame;

an air cleaner including a filter element disposed within the space formed in the hollow main frame, said air cleaner being divided into a dirty side and a clean side by the filter element;

an engaging member formed on the filter element, said engaging member extending substantially along the inner wall surface and engageable with the second rib; and

the first rib peripherally surrounds the filter element to provide a division wall with the second rib engaging the filter element to support the filter element,

wherein, as viewed in a sectional side elevation of the hollow main frame, a lower rib wall section of the first rib and a lower wall surface of the inner wall surface which is slanted downwardly toward a projection proximal portion of the lower rib wall section jointly define therebetween a downwardly recessed space disposed upstream of the lower rib wall section of the first rib with respect to the intake air flow.

13. The frame structure for a saddle vehicle, according to claim 12 , wherein a third rib projects inwardly into the space in the hollow main frame and is disposed between the first rib and the second rib in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

14. The frame structure for a saddle vehicle, according to claim 13 , wherein the filter element has a flange in a position overlapping the third rib as viewed along the direction of the intake air flow, the flange having a round end surface on a distal end thereof.

15. The frame structure for a saddle vehicle, according to claim 12 , wherein the hollow main frame has an upper opening defined in an upper portion thereof;

the upper opening is closed by an upper lid; and

the upper lid has a fourth rib disposed on an inner surface thereof and projecting in an overlapping relationship to the filter element as viewed along the direction of the intake air flow.

16. The frame structure for a saddle vehicle, according to claim 15 , wherein, as viewed in a sectional side elevation of the hollow main frame, the second rib is disposed downstream of the first rib with respect to the intake air flow and is located within a vertically projected range of the upper opening.

17. The frame structure for a saddle vehicle, according to claim 12 , wherein the hollow main frame has a water drain hole defined therein upstream of the filter element with respect to the intake air flow and positioned downwardly of at least an element filter.