Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
2000-07-14
2001-04-10
Swinehart, Ed (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
C440S056000
Reexamination Certificate
active
06213823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a trim-tilt device for a marine propulsion unit such as an outboard motor or inboard/outboard motor.
2. Description of the Related Art
Conventionally, the trim-tilt device for a marine propulsion unit has a cylinder device interposed between a hull and the propulsion unit which is tiltably supported by the hull. By controlling supply and discharge of hydraulic fluid from a hydraulic fluid supply/discharge device to a cylinder device or vice versa, the cylinder device is expanded and contracted to thereby trim and tilt the marine propulsion unit.
A prior art trim-tilt device for a marine propulsion unit is described in Japanese Patent Application No. 11-112856. This application provides a cylinder device for a trim-tilt device for a marine propulsion unit comprising a housing connected to one of a hull and a marine propulsion unit and which forms a large-diameter trim chamber. A cylinder is telescopically inserted into the trim chamber of the housing which forms a small-diameter tilt chamber. A large-diameter trim piston is fixed to an end portion of the cylinder within the trim chamber of the housing which partitions the trim chamber into a first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side. A piston rod is connected to the other of the hull and the marine propulsion unit and is telescopically inserted into the tilt chamber of the cylinder. A small-diameter tilt piston is fixed to an end of the piston rod within the tilt chamber of the cylinder which partitions the tilt chamber into a first tilt chamber of a piston rod accommodation side and a second tilt chamber of an anti piston rod accommodation side.
In the above-mentioned trim-tilt device for the marine propulsion unit disclosed in Japanese Patent Application No. 11-112856, during normal forward sailing, the load of an outboard motor and an external force of a forward driving force act in the direction which contracts the cylinder device. Thus, when the cylinder device expands (up) such that a discharging hydraulic pressure of the pump acts on the second trim chamber and the second tilt chamber (a lower chamber), the pressure-receiving area of a lower chamber side of the trim piston is larger than the pressure-receiving area of a lower chamber side of the tilt piston, so that a tilt-up operation is carried out after a trim-up operation. When the cylinder device is contracted (down) such that the discharging pressure hydraulic pressure of the pump acts on the first trim chamber and the second tilt chamber (an upper chamber), the pressure-receiving area of an upper chamber side of the tilt piston is larger than the pressure-receiving area of an upper chamber side of the trim piston, which is not intercepted by the cylinder, so that the trim-down operation is carried out after a tilt-down operation.
However, the cylinder's expansion (up) involves a disadvantage, such as when a tilt-up operation occurs before a trim-up operation, when an external force, such as a backward driving force during backward sailing or an uplifting force of a wave to raise a marine propulsion unit, acts in the direction for expanding the cylinder device. In the situation that the external force Fa acts, for expanding the cylinder device, the pump is driven and a switching valve is opened. In the situation that the discharging pressure Pa of the pump acts to the second trim chamber (the lower chamber), when the force of Fa is greater than that of Pa, namely, Fa/S<Pa (S: a pressure receiving area of a tilt piston), the piston rod of the tilt piston, to which Fa acts, moves ahead of the trim piston. At that time, a hydraulic pressure flow passage from the first tilt chamber to the pump absorption side is unlocked, since the switching valve is opened.
If the external force, as described above, that acts in the direction for expanding the cylinder device, such as a backward driving force during backward sailing or an uplifting force of a wave to raise a marine propulsion unit, is greater, a pressure in the pipe passage from the first tilt chamber to the pump absorption side becomes higher, the pump rotates at this pressure in the pipe passage. As the result of that, the discharge/absorption amount of the pump increases more than usual, so that an up-speed of trim/tilt becomes suddenly high.
SUMMARY OF THE INVENTION
The object of the invention is to ensure that a tilt-up operation is carried out after a trim-up operation, even when an external force acts in the direction that expands a cylinder device to a marine propulsion unit backward sailing or the like, in a trim-tilt device for a marine propulsion unit.
According to the present invention, there is disclosed a trim-tilt device for a marine propulsion unit, wherein a cylinder device is mounted between a hull and the marine propulsion unit freely tiltably supported by the hull. A hydraulic fluid is supplied from a hydraulic fluid supply/discharge device into the cylinder device and is discharged from the cylinder device into the hydraulic fluid supply/discharge device to thereby expand and contract the cylinder device and thereby trim and tilt the marine propulsion unit.
The cylinder device comprises:
a housing connected to one of the hull and marine propulsion unit to form a large-diameter trim chamber;
a cylinder telescopically inserted into the trim chamber and forming a small-diameter tilt chamber;
a large-diameter trim piston fixed to an end portion of the cylinder within the trim chamber of the housing and serving to partition the trim chamber into a first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side;
a piston rod being connected to the other of the hull and the marine propulsion unit that is telescopically inserted into the tilt chamber of the cylinder; and
a small-diameter tilt piston being fixed to an end portion of the piston rod within the tilt chamber of the cylinder and serving to partition the tilt chamber into a first tilt chamber of a piston rod accommodation side and a second tilt chamber of an anti piston rod accommodation side,
wherein a check valve for allowing the hydraulic fluid to flow from a pump to the first trim chamber and the first tilt chamber, and a relief valve, which is opened if the hydraulic pressure of the first trim chamber and the first tilt chamber becomes higher than a fixed value, are connect in parallel to a hydraulic fluid low passage connecting the first trim chamber and the first tilt chamber to the pump. When an external force acts in the direction for expanding the cylinder device to the marine propulsion unit, the cylinder device carries out an expansion operation so that the cylinder device can start the movement of the tilt piston after the movement of the trim piston is finished.
REFERENCES:
patent: 5718613 (1998-02-01), Nakamura
patent: 7-69288 (1995-03-01), None
patent: 7-69289 (1995-03-01), None
Nakamura Tamotsu
Orihara Keiji
Takayanagi Hisao
Toyoshima Omito
Orum & Roth
Showa Corporation
Swinehart Ed
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