Jet propelled watercraft

A jet propelled watercraft includes a vessel body, a jet propulsion mechanism, a bucket, and a controller. The jet propulsion mechanism is configured to propel the vessel body. The controller is configured and programmed to control a thrust of the jet propulsion mechanism to propel the vessel body. The bucket is configured to move to a retracted position spaced away from the jet of water ejected from the jet propulsion mechanism and a jet receiving position to receive the jet of water ejected from the jet propulsion mechanism. The controller is configured and programmed to change an increase rate of the thrust in accordance with a forward speed of the vessel body until the thrust is increased to a predetermined value after the bucket has been moved from the retracted position to the jet receiving position.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-226878, filed on Oct. 31, 2013. The entire disclosure of Japanese Patent Application No. 2013-226878 is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a jet propelled watercraft.

2. Description of the Related Art

To stabilize behavior of a vessel body when reducing the speed of a jet propelled watercraft, a method has been disclosed that, when the forward speed of the vessel is greater than a predetermined speed, thrust to reduce the speed of the vessel body is further reduced in comparison with when the forward speed of the vessel body is less than or equal to the predetermined speed (see U.S. Pat. No. 8,177,594).

However, according to the method described in U.S. Pat. No. 8,177,594, thrust is set in accordance with the forward speed at the start of reducing the speed. Hence, it is difficult to simultaneously implement a prompt speed reduction and a stabilized behavior of the vessel body. Specifically, where the predetermined speed is set to be somewhat high, the behavior of the vessel body is likely to be unstable when the forward speed is slightly less than the predetermined speed. This is because, in such a condition, the behavior of the vessel body easily becomes unstable, although the thrust is large.

By contrast, where the predetermined speed is set to be somewhat low, a prompt speed reduction cannot be implemented when the forward speed is slightly greater than the predetermined speed. This is because, in such a condition, the behavior of the vessel body is unlikely to be unstable, but thrust is small.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention have been conceived in view of the aforementioned situation. A preferred embodiment of the present invention provides a jet propelled watercraft that achieves both a prompt speed reduction and a stabilized behavior of a vessel body during the speed reduction.

A jet propelled watercraft according to a preferred embodiment of the present invention includes a vessel body, a jet propulsion mechanism, a controller, and a bucket. The jet propulsion mechanism is configured to propel the vessel body. The controller is configured and programmed to control a thrust of the jet propulsion mechanism to propel the vessel body. The bucket is configured to move to a retracted position spaced away from the jet of water ejected from the jet propulsion mechanism and a jet receiving position to receive the jet of water ejected from the jet propulsion mechanism. The controller is configured and programmed to change an increase rate of the thrust in accordance with a forward speed of the vessel body until the thrust is increased to a predetermined value after the bucket has been moved from the retracted position to the jet receiving position.

According to preferred embodiments of the jet propelled watercraft described below, a jet propelled watercraft is provided that achieves both a prompt speed reduction and a stabilized behavior of a vessel body during the speed reduction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, explanation will be hereinafter made for a schematic structure of a jet propelled watercraft1according to preferred embodiments of the present invention.FIG. 1is a cross-sectional view of the schematic structure of the jet propelled watercraft1according to a preferred embodiment. In the following explanation, the terms “front”, “rear”, “right” and “left” are defined with reference to the point of view of a vessel operator seated on a seat7.

The jet propelled watercraft1preferably is so-called a personal watercraft (PWC), for example. The jet propelled watercraft1includes a vessel body2, an engine3, a fuel tank4, a jet propulsion mechanism5, a bucket6, the seat7, a steering handle8, a speed sensor9, and a controller10.

The vessel body2includes a deck2aand a hull2b. An engine compartment2cis provided inside the vessel body2. The engine compartment2caccommodates the engine3, the fuel tank4and so forth. The engine3includes a crankshaft31extending in the back-and-forth direction.

The jet propulsion mechanism5is configured to generate thrust to propel the vessel body2by a driving force from the engine3. The jet propulsion mechanism5is configured to suck in and eject water that surrounds the vessel body2. The jet propulsion mechanism5includes an impeller shaft50, an impeller51, an impeller housing52, a jet nozzle53, and a steering nozzle54.

The impeller shaft50is disposed so as to extend rearward from the engine compartment2c. The front portion of the impeller shaft50is coupled to the crankshaft31through a coupling member36. The rear portion of the impeller shaft50extends into the impeller housing52through a water suction member2eof the vessel body2. The impeller housing52is connected to the rear portion of the water suction member2e.

The impeller51is attached to the rear portion of the impeller shaft50. The impeller51is disposed inside the impeller housing52. The impeller51is configured to be rotated together with the impeller shaft50and suck water into the impeller housing52through the water suction member2e. The impeller51is configured to rearwardly eject the sucked in water out of the jet nozzle53. The jet nozzle53is disposed rearward of the impeller housing52. A support bracket53ato support the bucket6is fixed to the jet nozzle53.

The steering nozzle54is disposed rearward of the jet nozzle53. The steering nozzle54includes a jet port54a. A jet of water that propels the vessel body2is ejected from the jet port54arearward. The steering nozzle54is mounted so as to be pivotable right and left. The steering nozzle54is configured to switch the ejection direction of the jet of water between right and left in response to the operation of the steering handle8. The steering nozzle54is preferably configured to switch the ejection direction between up and down in response to the operation of a trim adjustor switch mounted to the steering handle8.

The bucket6is disposed rearward of the jet propulsion mechanism5. The bucket6is supported by the support bracket53a, while being pivotable up and down about a pivot shaft6aextending right and left. The bucket6is configured to move to a position spaced away from the jet of water ejected from the jet port54a(hereinafter referred to as “a retracted position”) and a position to receive the jet of water ejected from the jet port54a(hereinafter referred to as “a jet receiving position”). In the present preferred embodiment, the jet receiving position is a concept that includes: a position in which thrust does not act on the vessel body2(hereinafter referred to as “a neutral position”, seeFIG. 1); and a position in which rearward thrust acts on the vessel body2(hereinafter referred to as “a rearward thrust position”). When the bucket6is located in the retracted position, the jet of water mainly flows rearward and the vessel body2is thus moved forward. Therefore, the retracted position is expressed as a position in which forward thrust acts on the vessel body2(hereinafter referred to as “a forward thrust position”). On the other hand, when the bucket6is located in the neutral position, the forward thrust and the rearward thrust are cancelled out. Therefore, when the vessel body2is in a state of not being moved, the unmoved state is maintained. When the bucket6is located in the rearward thrust position, the jet of water mainly flows forward. When the bucket6is located in the rearward thrust position and the vessel body2is moving forward, the vessel body2is reduced in its speed. On the other hand, when the bucket6is located in the rearward thrust position and the vessel body2is not presently being moved, the vessel body2begins to move backwards.

The seat7is attached to the deck2a. The seat7is disposed over the engine3. The steering handle8is disposed forward of the seat7. The steering handle8is an operating member configured to steer the vessel body2. The steering handle8is equipped with a throttle operating member8aand a shift operating member8b.

The throttle operating member8ais an operating member configured to regulate the throttle opening degree of the engine3. A vessel operator regulates the thrust of the jet propulsion mechanism5by changing the operating amount of the throttle operating member8a.

The shift operating member8bis movable to a forward shift position, a rearward shift position, and a neutral shift position. When the shift operating member8bis switched into the forward shift position, the bucket6is configured to be moved to the retracted position. When the shift operating member8bis switched into either the neutral shift position or the rearward shift position, the bucket6is configured to be moved to the jet receiving position (the neutral position or the rearward thrust position).

The speed sensor9is attached to the hull2band disposed under the jet nozzle53. In the present preferred embodiment, a paddle turbine is used as the speed sensor9. It should be noted that for the speed sensor9, it is possible to use a rotation speed sensor configured to measure the rotation speed of the crankshaft31of the engine3, a receiver configured to receive a navigation signal from a navigation satellite of GNSS (Global Navigation Satellite System) or so forth.

The controller10includes a computer including a CPU, a memory and so forth. The controller10is configured and programmed to control the thrust of the jet propulsion mechanism5to propel the vessel body2.

FIG. 2is a block diagram representing a configuration of the controller10.FIGS. 3A to 3Gare charts respectively exemplifying a transition in the operating amount V of the throttle operating member8a, a transition in the position of the shift operating member8b, a transition in the target throttle opening degree TG, a transition in the forward speed S, a transition of the regulation coefficient R, a transition of the throttle opening degree TH, and a transition of the thrust P.

As shown inFIG. 2, the controller10includes a target throttle opening degree determining unit101, a regulation coefficient determining unit102, and a throttle opening degree regulating unit103.

The target throttle opening degree determining unit101is configured to detect the operating amount V of the throttle operating member8ashown inFIG. 3A. In the example ofFIG. 3A, the operating amount V is reduced from 100 (maximum value) to 0 (minimum value) in a period from a clock time T1 to a clock time T2, and is then increased from 0 to 100 in a period from a clock time T5 to a clock time T6. It should be noted that the operating amount V is a value that is variable in response to the operation by the vessel operator. The target throttle opening degree determining unit101is configured to detect the position of the shift operating member8bshown inFIG. 3B. In the example ofFIG. 3B, the shift operating member8bis moved from the forward shift position to the rearward shift position in a period from a clock time T3 to a clock time T4. In conjunction, the bucket6(seeFIG. 1) is moved from the retracted position to the jet receiving position.

The target throttle opening degree determining unit101is configured and programmed to determine the target throttle opening degree TG shown inFIG. 3Cbased on the operating amount V of the throttle operating member8aand the position of the shift operating member8b. The target throttle opening degree TG is the maximum value of the throttle opening degree TH required to obtain the thrust desired by the vessel operator. The target throttle opening degree determining unit101is configured and programmed to determine the target throttle opening degree TG regardless of the magnitude of the forward speed S. In the example ofFIG. 3C, the target throttle opening degree TG is reduced from a first target opening degree TG1 to an idling opening degree TGa in a period from the clock time T1 to the clock time T2, and is then increased from the idling opening degree TGa to a second target opening degree TG2 in a period from the clock time T5 to the clock time T6. The idling opening degree TGa is set to be a value required to cause the engine3to idle. Because the operating amount V of the throttle operating member8ais increased to 100 as shown inFIG. 3E, the first target opening degree TG1 is set as the maximum value of the throttle opening degree TH where the bucket6is located in the retracted position, whereas the second target opening degree TG2 is set as the maximum value of the throttle opening degree TH where the bucket6is located in the jet receiving position in the example ofFIG. 3C.

The target throttle opening degree determining unit101is configured and programmed to output the determined target throttle opening degree TG to the throttle opening degree regulating unit103.

The regulation coefficient determining unit102is configured and programmed to detect the forward speed S shown inFIG. 3D. The forward speed S is gradually reduced at, and after, the clock time T3 when the bucket6begins to be moved toward the jet receiving position. As shown inFIG. 3E, the regulation coefficient determining unit102is configured and programmed to determine the regulation coefficient R in accordance with the forward speed S in a period from the clock time T5 to a clock time T7, and configured and programmed to keep the regulation coefficient R at 1.0 (maximum value) at, and before, the clock time T5 and at, and after, the clock time T7. The clock time T5 is a clock time when the target throttle opening degree TG begins to be increased from the idling opening degree TGa to the second target opening degree TG2 after the bucket6has been moved to the jet receiving position. The clock time T7 is a clock time when the target throttle opening degree TG reaches the second target opening degree TG2.

FIG. 4represents a chart exemplifying a relationship between the forward speed S and the regulation coefficient R. As shown inFIG. 4, when the forward speed S is greater than a lower limit S1 and less than an upper limit S2, the regulation coefficient determining unit102is configured and programmed to reduce the regulation coefficient R in accordance with increase in the forward speed S. On the other hand, when the forward speed S is less than or equal to the lower limit S1, the regulation coefficient determining unit102is configured and programmed to fix the regulation coefficient R at 1.0 (maximum value). Yet, on the other hand, when the forward speed S is greater than or equal to the upper limit S2, the regulation coefficient determining unit102is configured and programmed to fix the regulation coefficient Rat 0.2 (minimum value). It should be noted that the minimum value (herein set to be 0.2) of the regulation coefficient R can be arbitrarily set.

The regulation coefficient determining unit102is configured and programmed to output the determined regulation coefficient R to the throttle opening degree regulating unit103.

The throttle opening degree regulating unit103is configured and programmed to calculate the throttle opening degree TH shown inFIG. 3Fby multiplying the target throttle opening degree TG and the regulation coefficient R. In the example ofFIG. 3F, the throttle opening degree TH is reduced from the first target opening degree TG1 to the idling opening degree TGa in a period from the clock time T1 to the clock time T2, and is then kept at the idling opening degree TGa in a period from the clock time T2 to the clock time T5. Thereafter, the throttle opening degree TH is increased from the idling opening degree TGa to the second target opening degree TG2 in accordance with a reduction in the forward speed S in a period from the clock time T5 to the clock time T7, and is then kept at the second target opening degree TG2.

The throttle opening degree regulating unit103is configured and programmed to control the driving force of the engine3by outputting the calculated throttle opening degree TH to the engine3. As a result, the rotation speed of the impeller51is regulated, and as shown inFIG. 3G, the thrust P of the jet propulsion mechanism5is regulated. In the example shown inFIG. 3G, the thrust P is reduced from a first thrust P1 to an idling thrust Pa in a period from the clock time T1 to the clock time T2, and is then kept at the idling thrust Pa in a period from the clock time T2 to the clock time T5. Thereafter, the thrust P is increased from the idling thrust Pa to a second thrust P2 in accordance with a reduction in the forward speed S in a period from the clock time T5 to the clock time T7, and is then kept at the second thrust P2.

Thus, the controller10is configured and programmed to change the increase rate of the thrust P in accordance with the forward speed S until the thrust P is increased to the second thrust P2 (an exemplary predetermined value) after the bucket6has been moved from the retracted position to the jet receiving position (i.e., in a period from the clock time T5 to the clock time T7). Thus, the speed of the vessel body2is reduced with the necessary and sufficient thrust P in a period from the clock time T5 to the clock time T7. Hence, the vessel body2is promptly reduced in its speed while being stabilized in its behavior.

The exemplary preferred embodiments of the present invention have been described above. However, the present invention is not limited to the aforementioned exemplary preferred embodiments, and a variety of changes can be herein made without departing from the scope of the present invention.

In the aforementioned exemplary preferred embodiments, the controller10is preferably configured and programmed to gradually increase the increase rate of the thrust P by gradually increasing the regulation coefficient R in accordance with a reduction in the forward speed S until the thrust P is increased to the second thrust P2. However, until the thrust P is increased to the second thrust P2, the controller10may be configured and programmed to gradually reduce the increase rate of the thrust P in accordance with the reduction in the forward speed S, as shown inFIG. 5, or alternatively, may be configured and programmed to keep the increase rate constant.

In the aforementioned exemplary preferred embodiments, the controller10is preferably configured and programmed to determine the regulation coefficient R in accordance with the chart shown inFIG. 4. However, the relationship between the forward speed S and the regulation coefficient R can be arbitrarily set.