TECHNICAL FIELD

The present invention relates to a fuel tank structure.

BACKGROUND ART

Heretofore, as a fuel cap that closes a fuel supply port of a fuel tank, there has been known a fuel cap comprising a pressure adjusting valve that adjusts a pressure in the fuel tank (e.g., see Patent Literature 1).

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Patent No. 5630420

SUMMARY OF INVENTION

Technical Problem

Patent Literature 1 discloses a structure that an evaporative fuel inside a fuel tank exits and air outside the fuel tank enters through a space provided with a pressure adjusting valve in a cap body of a fuel cap, holes of an outer torque mechanism and a gap between the torque mechanism and a lid body. Consequently, in a case where the fuel tank is attached to a vehicle body in an uncovered manner as in a motorcycle, mud, water, dust or the like easily enters the fuel tank. There is also a problem that a leakage region of the fuel in the fuel tank broadens when the vehicle falls.

It is an object of the present invention to provide a fuel tank structure that makes it difficult for mud, water, dust or the like to enter a fuel tank and that can restrict a fuel leakage path when a vehicle falls.

Solution to Problem

The entire content of Japanese Patent Application No. 2017-176550 filed in Sep. 14, 2017 is incorporated herein.

According to the present invention, provided is a fuel tank structure comprising, in a fuel cap (92), a cap body (111) mounted to a fuel supply port (91) of a fuel tank (31), and a pressure adjusting device (117) provided in the cap body (111) to adjust a pressure in the fuel tank (31), wherein in the fuel cap (92), a hermetically closed space (124a) in which the pressure adjusting device (117) is accommodated is formed, and the hermetically closed space (124a) communicates with an exterior of the fuel tank (31) via a breather tube (101).

In the above invention, the breather tube (101) may have an open end inserted in a stem pipe (99).

Furthermore, in the above invention, the cap body (111) and a retainer (113) attached to the cap body (111) may form a housing (124), the hermetically closed space (124a) may be formed in the housing (124), the breather tube (101) may be connected directly to the retainer (113), and a space between the retainer (113) and the cap body (111) may be sealed.

Additionally, in the above invention, a cap outer (116) may be fitted in and thereby attached to an outer side of the cap body (111), a fuel tray (106) may be provided around the fuel supply port (91) of the fuel tank (31), a tray peripheral wall (106a) may be formed in the fuel tray (106) to surround the fuel supply port (91), and a dust seal portion (106b) extending radially outward from the tray peripheral wall (106a) may be fitted in an inner peripheral surface of an outer peripheral wall (116e) formed in the cap outer (116).

Furthermore, in the above invention, the fuel tank (31) may comprise a tank cover (94) that covers a periphery of the fuel supply port (91), a cylindrical portion (94a) in which the outer peripheral wall (116e) of the cap outer (116) is inserted may be formed in the tank cover (94), the cylindrical portion (94a) may be formed on a radially inner side of an outermost peripheral portion (116f) of the cap outer (116), and a lower edge of the outermost peripheral portion (116f) of the cap outer (116) may be located below an upper edge of the cylindrical portion (94a).

Advantageous Effects of Invention

According to the present invention, in a fuel cap, a hermetically closed space in which a pressure adjusting device is accommodated is formed, and the hermetically closed space communicates with an exterior of a fuel tank via a breather tube. Consequently, a gas can exit and enter the fuel tank only through the breather tube to adjust a pressure in the fuel tank. This can make it difficult for mud, water, dust or the like to enter the fuel tank, and can restrict a fuel leakage path when a vehicle falls.

Furthermore, in the above invention, the breather tube has an open end inserted in a stem pipe. This can further inhibit the mud, water, dust or the like from entering the fuel tank, and can further restrict the fuel leakage path when the vehicle falls.

Additionally, in the above invention, the cap body and a retainer attached to the cap body form a housing, the hermetically closed space is formed in the housing, the breather tube is connected directly to the retainer, and a space between the retainer and the cap body is sealed. Consequently, the space between the retainer and the cap body is sealed, so that an interior of the housing can be easily formed as the hermetically closed space, and gas leakage from the housing itself to the exterior of the fuel tank can be prevented.

Furthermore, in the above invention, a fuel tray is provided around the fuel supply port of the fuel tank, a tray peripheral wall is formed in the fuel tray to surround the fuel supply port, and a dust seal portion extending radially outward from the tray peripheral wall is fitted in an inner peripheral surface of an outer peripheral wall formed in a cap outer. Consequently, the dust seal portion of the fuel tray is fitted in the outer peripheral wall of the cap outer, so that it can be difficult for the mud, water, dust or the like to enter the fuel tank.

Additionally, in the above invention, the fuel tank comprises a tank cover that covers a periphery of the fuel supply port, a cylindrical portion in which the outer peripheral wall of the cap outer is inserted is formed in the tank cover, the cylindrical portion is formed on a radially inner side of an outermost peripheral portion of the cap outer, and a lower edge of the outermost peripheral portion of the cap outer is located below an upper edge of the cylindrical portion. Therefore, the outermost peripheral portion of the cap outer and the cylindrical portion of the tank cover can form a labyrinth structure. Consequently, it is possible to prevent permeation of the mud, water, dust or the like into the fuel cap, and it is possible to make it difficult for the mud, water, dust or the like to enter the fuel tank during opening/closing of the fuel cap.

