Marine propulsion – Engine – motor – or transmission control means – For engine speed
Reexamination Certificate
2001-08-02
2003-05-27
Sotelo, Jesus D. (Department: 3617)
Marine propulsion
Engine, motor, or transmission control means
For engine speed
C440S001000, C114S1440RE
Reexamination Certificate
active
06568968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a jet-propulsion watercraft which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a jet-propulsion watercraft, which can maintain steering capability even when the throttle is operated in the closed position and propulsion force is thereby reduced, and a cruising speed calculating device suitable for the watercraft.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercraft (PWC) have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom of a hull and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
In the personal watercraft, in association with a steering handle of a general bar type, a steering nozzle provided behind the outlet port of the water jet pump is swung either to the right or left, to change the ejecting direction of the water to the right or to the left, thereby turning the watercraft.
A deflector is retractably provided behind the steering nozzle for blocking the water ejected from the steering nozzle. The deflector is moved downward to deflect the ejected water forward, and as the resulting reaction, the personal watercraft moves rearward. In some watercraft, in order to move rearward, a water flow is formed so as to flow from an opening provided laterally of the deflector along a transom board to reduce the water pressure in an area behind the watercraft.
In the above-described personal watercraft, when the throttle is moved to a substantially fully closed position and the water ejected from the water jet pump is thereby reduced, during forward movement and rearward movement, the propulsion force necessary for turning the watercraft is correspondingly reduced, and the steering capability of the watercraft is therefore reduced until the throttle is re-opened.
To solve the above-described condition with a mechanical structure, the applicant disclosed a jet-propulsion personal watercraft comprising a steering component for an auxiliary steering system which operates in association with the steering handle in addition to a steering nozzle for the main steering system in Japanese Patent Application No. Hei. 2000-6708.
SUMMARY OF THE INVENTION
The present invention addresses the above-described condition, and an object of the present invention is to provide a jet-propulsion watercraft, which can maintain steering capability according to the cruising speed thereof even when the operation which closes the throttle (hereinafter referred to as “throttle-close operation”) is performed and the amount of water ejected from a water jet pump is thereby reduced, and a cruising speed calculating device suitable for the watercraft.
According to the present invention, there is provided a jet-propulsion watercraft comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; an engine for driving the water jet pump; a steering operation means that operates in association with a steering nozzle of the water jet pump; a steering position sensor for detecting a predetermined steering position of the steering operation means; an engine speed sensor for detecting an engine speed of the engine; a cruising speed calculating means for calculating a cruising speed of the watercraft based on the engine speed detected by the engine speed sensor; and an electric control unit, wherein the electric control unit is adapted to increase the engine speed while a result detected by the steering position sensor is the predetermined steering position and a value calculated by the cruising speed calculating means is within a predetermined speed range.
According to the jet-propulsion watercraft, the engine speed is increased while the watercraft is steered, this operation is detected by the steering position sensor, and while the cruising speed calculated by the cruising speed calculating means based on the engine speed detected by the engine speed sensor is within a predetermined speed range. Therefore, the water sufficient to turn the watercraft is ejected from the water jet pump, and the steering capability can be maintained even when the throttle-close operation is performed.
Thus, a personal watercraft without a so-called cruising speed sensor can be placed in a steered state adapted to the actual cruising speed. In addition, since the cruising speed employed in the control process can be calculated from the engine speed, the personal watercraft is capable of obtaining the cruising speed without the normal cruising speed sensor, for example, the conventional hydraulic cruising speed sensor which tends to be clogged with contamination in water.
Herein, control for increasing the engine speed is referred to as “steering assist mode control”, and the “throttle-close operation” means that operation is performed to bring the throttle toward a closed position by a predetermined amount or more.
In the jet-propulsion watercraft, the cruising speed calculating means may include a speed conversion table that stores relationship between the engine speed and the cruising speed and is adapted to refer to the speed conversion table based on the detected engine speed to read out the cruising speed.
In the jet-propulsion watercraft, the cruising speed calculating means may further include: an offset table that stores an offset value used for offsetting the cruising speed stored in the speed conversion table according to a degree of acceleration/deceleration of the engine; and an obtaining means for obtaining the degree of acceleration/deceleration of the engine, and the cruising speed read from the speed conversion table can be offset according to the degree of acceleration/deceleration of the engine. Specifically, the cruising speed calculating means offsets the cruising speed by addition/subtraction based on the offset value read from the offset table and the cruising speed read from the speed conversion table. Thereby, a more accurate cruising speed in view of the inertia of the watercraft can be obtained.
In the jet-propulsion watercraft, the obtaining means for obtaining the degree of acceleration/deceleration of the engine may comprise: an engine speed memory for sequentially storing the engine speed detected by the engine speed sensor; a calculating means for calculating a difference value between two engine speeds stored in the engine speed memory; a difference value memory for sequentially storing the calculated difference value; and a cumulating means for cumulating the difference values stored in the difference value memory, and the degree of acceleration/deceleration of the engine can be calculated based on a cumulated value. The term “sequentially” is herein defined as “in time sequence”. It should be noted that all of the engine speeds detected by the engine speed sensor in predetermined time cycles may be stored in the engine speed memory or they may be partially stored therein. Further, the engine speed sensor may detect the engine speed for every control clock or partially detect the engine speed.
The degree of acceleration/deceleration of the engine may be obtained indirectly by the calculation as described above, or otherwise may be obtained directly from a transducer provided on a crankshaft of the engine.
The jet-propulsion watercraft may further contain a throttle-close operation sensor for detecting throttle-close operation, and the engine speed can be increased while the steering operation is detected by the steering position sensor, the throttle-close operation is detected by the throttle-close operation sensor, and the value calculated by the cruising speed calculating means is within a predetermined speed range.
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Kawasaki Jukogyo Kabushiki Kaisha
Sotelo Jesus D.
LandOfFree
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