The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-249277, filed Aug. 20, 2001, the entire contents of are which hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an exhaust structure for a jet propulsion boat in which exhaust gas from the engine is discharged into the pump chamber by providing a jet propulsion machine inside a pump chamber of the hull and connecting an exhaust pipe to the pump chamber.
2. Description of Background Art
The jet propulsion boat is a vessel provided with a jet pump mounted at the rear portion of the hull, and propelled by drawing in water from the vessel bottom by driving the jet pump by the engine, and forcing the water rearwardly.
An exhaust structure for a jet propulsion boat has been disclosed in Japanese Patent Laid-Open No. 282840/2000 entitled xe2x80x9cexhaust structure for a jet propulsion boatxe2x80x9d. The means to lower the exhaust noise generated in the jet propulsion boat is disclosed in the same publication. According to this technology, a resonator for sound-deadening is provided on the exhaust pipe connected to the engine. Exhaust noise is resonated by means of the resonator, so that the exhaust noise is reduced.
In the above disclosure, a part of the exhaust pipe is formed into a substantially U-shape which is upwardly convex in order to prevent water from entering from the outlet port of the exhaust pipe into the engine side. Forming a part of the exhaust pipe into a substantially U-shape makes the length of the exhaust pipe relatively long. Thus, in order to attenuate the noise in the elongated exhaust pipe, the length of the resonator must be long relative to the exhaust pipe.
Therefore, in order to mount the elongated resonator inside the hull, a sufficient storage space must be secured.
However, the space in the hull is limited. Thus, the layout of the required accessories of the boat which are also to be mounted inside the hull must be considered, in order to secure the relatively large storage space required for the resonator in this limited space. In other words, securing a storage space for and mounting the resonator, which is required for reducing the exhaust noise of the jet propulsion boat, has proved to be difficult.
Accordingly, it is an object of the present invention to provide an improved exhaust structure for a jet propulsion boat that addresses the above problem.
In order to solve the problem, the present invention provides an exhaust structure for a jet propulsion boat in which a tunnel-shaped pump chamber is provided at the rear portion of the hull, a jet propulsion machine is provided in the pump chamber, an engine is connected to the jet propulsion machine for driving the boat, and an exhaust port of the exhaust pipe extending from the engine is faced toward the pump chamber. Further, a resonator for sound-deadening is disposed in the pump chamber, and the exhaust pipe is brought into communication with the resonator.
In this case, since the jet propulsion machine is disposed at the center of the tunnel-shaped pump chamber, a space is left in the vicinity of the wall surfaces of the top wall and the left and right walls of the pump chamber as a dead space.
Therefore, the resonator for sound-deadening can be mounted effectively in the dead space in the pump chamber. Therefore, the difficulty of securing a storage space in the boat for the resonator is eliminated.
The invention also includes an exhaust port disposed in the resonator by passing the exhaust pipe through the peripheral wall of the resonator, and an opening provided on the bottom wall of the resonator at the location facing upwardly toward the exhaust pipe, and downwardly toward pump chamber.
The exhaust port is disposed in the resonator and an opening is formed on the bottom wall of the resonator at the location facing toward the pump chamber. Therefore, exhaust gas discharged from the exhaust port and cooling water discharged together with exhaust gas can be conducted effectively out through the opening on the bottom of the resonator.
The opening is divided into a first and a second opening by a supporting beam, and a valve body is attached on the supporting beam so that the first and the second openings can be opened and closed by a pair of flaps provided on the valve body.
The first and the second openings in the resonator can be open and closed individually by the flaps. By providing separate individual flaps, the size of the flaps may be reduced, which allows the first and the second openings to be quickly closed by the respective flaps. Quick closing of the first and the second openings by the flaps helps to prevent water from entering the openings.
Further, the supporting beam of the present invention is provided with a guide portion of V-shaped or substantially V-shaped cross section projecting toward the exhaust port.
Since the supporting beam is provided with a guide portion of V-shaped or substantially V-shaped cross section projecting toward the exhaust port, exhaust gas and cooling water discharged together with exhaust gas can be guided via the guide portion and conducted smoothly to the first and second openings.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.