Patent Description:
Conventionally, a reduction reverse gear for a marine vessel such as a fishing boat includes a forward/reverse rotation switching mechanism (forward/reverse rotation clutch) which switches rotation power of an engine mounted on a hull to forward, neutral or reverse output and transmits it to a propeller, a forward/reverse switching valve to control a switching operation of the forward/reverse rotation switching mechanism, and a trolling device which controls pressure of working oil for the forward/reverse rotation switching mechanism. By causing the forward/reverse rotation switching mechanisms to make a slip engagement (half-clutch engagement), the propeller is rotated at a low speed while the engine is kept at a constant speed, a low speed propulsion such as trolling is performed with the propeller rotating at a low speed while an engine speed is kept constant (see, for example, Patent Literature <NUM>).

Patent Literature <NUM>: <CIT>. The cited patent literature discloses a hydraulic control system for adjusting the hydraulic pressure of the front and reverse clutch. It discloses a proportional solenoid valve for varying the pilot pressure of the low-speed valve. A direct electromagnetic valve for switching the pilot pressure supply circuit is provided so as to move the low-speed valve to the high-pressure adjustment position. Prior art document "<NPL>" discloses a structure and control circuit of slow speed reversing machine as well as aspects regarding the reduction of inspection maintenance. It discloses a gear for marine vessels with electronic controllers including various characteristics, e.g. high pressure oil being applied to activate the clutch and the measurement of the clutch hydraulic pressure using a pressure sensor.

However, in such type of reduction reverse gear, for example a common clutch connection control has been performed when switching the forward or reverse rotation, regardless of the size of each of clutches in the forward/reverse rotation switching mechanism (forward and reverse rotation clutches), and it has never suggested any attempts aimed at optimization of clutch connection control for each of clutches.

In light of the above mentioned circumstance, the technical problem of the present invention is to provide an improved reduction reverse gear.

The invention of claim <NUM> is a reduction reverse gear for marine vessel including a hydraulic clutch-type forward/reverse rotation switching mechanism, configured to convert rotation power of a main engine mounted on a hull to an output of forward rotation, neutral, or reverse rotation and to transfer the output to a propeller, wherein neutral represents a state in which no rotation power is transmitted to the output,,a forward/reverse rotation switching valve which is a three-position switching type including a forward rotation position, a neutral position and a reverse rotation position and is configured to control switching operation of the forward/reverse rotation switching mechanism, and a trolling device that regulates and controls the pressure of a working oil flowing toward the forward/reverse rotation switching mechanism, wherein the reduction reverse gear is configured such that: when the forward/reverse rotation switching valve is switched to the forward rotation position or the reverse rotation position during normal propulsion, wherein during normal propulsion the adjustment of the engine speed is made by means of a throttle lever, the trolling device is configured to control a pattern that reduces the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism so that the pattern is different between when the forward/reverse rotation switching valve is in the forward rotation position and when the forward/reverse rotation switching valve is in the reverse rotation position; and the reduction reverse gear comprises an operation detection member configured to detect an operation state of the forward/reverse rotation switching valve; and when the operation detection member detects that the forward/reverse rotation switching valve is in the neutral position during normal propulsion, the trolling device is configured to control the working oil so that the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism is not reduced.

According to a preferred embodiment according to the present invention the trolling device comprises a pressure reducing valve configured to reduce the pressure of the working oil and supplies the pressure reduced working oil to the forward/reverse rotation switching mechanism, a proportional valve configured to control output pressure of the working oil output from the pressure reducing valve, and a direct connection valve configured to turn working oil supply to the proportional valve on or off, and the trolling device is configured to control the pattern that reduces the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism so as to be different by changing a working pattern of the proportional valve.

According to a further preferred embodiment according to the present invention during transition to low speed propulsion, wherein the propeller is rotated at low speed while the engine is kept at a constant speed, a feedback control is configured to be performed based on a rotation speed of the propeller after the trolling device linearly increases the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism.

According to a further preferred embodiment according to the present invention the trolling device includes a pressure reducing valve configured to reduce the pressure of the working oil and supply the pressure reduced working oil to the forward/reverse rotation switching mechanism, a proportional valve configured to control output pressure of the working oil output from the pressure reducing valve, and a direct connection valve configured to turn working oil supply to the proportional valve on or off; and when the operation detection member detects that the forward/reverse rotation switching valve is in a neutral position during normal propulsion, the trolling device is configured to control the working oil so that the direct connection valve turns off the working oil supply to the proportional valve, and the pressure reducing valve is configured to deliver the working oil to the forward/reverse rotation switching mechanism without reducing the pressure of the working oil.

The reduction reverse gear for marine vessel according to the present invention wherein the reduction reverse gear may include a trolling priority member configured to operate to fully close the pressure reducing valve in an event where an error such as a communication failure occurs during low speed propulsion.

According to the present invention, when the forward/reverse rotation switching valve is switched to a forward rotation position or a reverse rotation position during normal propulsion, the trolling device controls a pattern that reduces pressure of working oil flowing toward the forward/reverse rotation switching mechanism so that the pattern is different between when the forward/reverse rotation switching valve is in the forward rotation position and when the forward/reverse rotation switching valve is in the reverse rotation position. So, for example, even when the size of the forward/reverse rotation switching mechanism (forward rotation clutch and reverse rotation clutch) are different from each other, this makes it easy to set pressure of working oil, working oil supply rate, and the like according to the forward/reverse rotation switching mechanism (forward rotation clutch and reverse rotation clutch). Therefore, it is possible not only to optimize a connection speed of the forward/reverse rotation switching mechanism (forward rotation clutch and reverse rotation clutch), but also to mitigate shock caused by connection of the forward/reverse rotation switching mechanism(forward rotation clutch and reverse rotation clutch) at the forward/reverse rotation switching.

Now, some specific embodiments of the present invention will be described below with reference to the drawings (<FIG>). As shown in <FIG>, a fishing boat <NUM>, which is a marine vessel, includes a hull <NUM>, a cabin <NUM> located on a top of the hull at the center side thereof, a rudder <NUM> on a bottom of the hull <NUM> at an aft side thereof, and a propeller <NUM> located on the bottom of the hull <NUM> at the aft side thereof in front of the rudder <NUM>. The cabin <NUM> has a navigation unit inside. Inside the cabin <NUM>, the navigation unit is provided with a forward/reverse rotation lever <NUM> as a forward/reverse control device which switches a traveling direction of the hull <NUM> between forward and backward, a throttle lever <NUM> to set and hold an engine speed of an engine <NUM>, a trolling switch <NUM> to set a turning on/off of trolling propulsion (low speed propulsion), and a trolling dial <NUM> and the like to set a trolling speed (low speed propulsion speed) (see <FIG>). Inside the cabin <NUM>, although not shown in the drawings, a steering handle is provided to change the traveling direction of the hull <NUM> in a right and left directions by steering it.

A propulsion shaft <NUM>, which rotates the propeller <NUM>, is supported at the aft side on the bottom of the hull <NUM>. The propeller <NUM> is attached to an end on a protruding side of the propulsion shaft <NUM>. In the hull <NUM>, there is provided the engine <NUM> as a main engine which is a driving source of the propeller <NUM> and a reduction reverse gear <NUM> to transmit rotation power of the engine <NUM> to the propeller <NUM> via the propulsion shaft <NUM>. The propeller <NUM> is forced to rotate by the rotation power transmitted from the engine <NUM> to the propulsion shaft <NUM> via the reduction reverse gear <NUM>.

As shown in <FIG>, a housing <NUM>, which is an outer casing of the reduction reverse gear <NUM>, has an input shaft <NUM> connected to a flywheel <NUM> of the engine <NUM> via a damper coupling <NUM> and an output shaft <NUM> connected to the propulsion shaft <NUM> via coupling <NUM>. The input shaft <NUM> is rotatably supported by upper portions of the housing <NUM>. The input shaft <NUM> protrudes in a forward direction from a front side of the upper portion of the housing <NUM>. The output shaft <NUM> is rotatably supported by lower portions of the housing <NUM>. The output shaft <NUM> protrudes in a backward direction from a rear side of the lower portion of the housing <NUM>. The input shaft <NUM> and the output shaft <NUM> extend in parallel inside the housing <NUM>. The housing <NUM> houses a forward rotation clutch <NUM> which connects and disconnects power transmitted in the forward (advance) direction from the input shaft <NUM> to the output shaft <NUM> and a reverse rotation clutch <NUM> which connects and disconnects power transmitted in the reverse (retreat) direction from the input shaft <NUM> to the output shaft <NUM>. The forward rotation clutch <NUM> and the reverse rotation clutch <NUM> constitute a forward/reverse rotation switching mechanism <NUM>.

The forward rotation clutch <NUM> and the reverse rotation clutch <NUM> are of a wet-multi-disc hydraulic friction type. The forward rotation clutch <NUM> is located on the input shaft <NUM>. A forward rotation gear 15a is provided in the forward rotation clutch <NUM> on an upstream side in a direction of power transmitted from the engine <NUM>. A forward rotation reduction gear 15b is provided in the forward rotation clutch <NUM> on a downstream side in the direction of power transmitted from the engine <NUM>. The forward rotation gear 15a is fixed to the input shaft <NUM>. The forward rotation reduction gear 15b is rotatably fitted to the input shaft <NUM>.

The reverse rotation clutch <NUM> is located on a reverse rotation shaft <NUM> extending in parallel with the input shaft <NUM>. A reverse rotation gear 16a is provided in the reverse rotation clutch <NUM> on an upstream side in a direction of power transmitted from the engine <NUM>. A reverse rotation reduction gear 16b is provided in the reverse rotation clutch <NUM> on a downstream side in the direction of power transmitted from the engine <NUM>. The reverse rotation gear 16a is fixed to the reverse rotation shaft <NUM>. The reverse rotation reduction gear 16b is rotatably fitted to the reverse rotation shaft <NUM>.

The forward rotation gear 15a always meshes with the reverse rotation gear 16a. The forward rotation reduction gear 15b and the reverse rotation reduction gear 16b always mesh with a reduction output gear <NUM> fixed to the output shaft <NUM>. The forward rotation reduction gear 15b, the reverse rotation reduction gear 16b, and the reduction output gear <NUM> constitute a reduction gear mechanism with a constant reduction ratio. Rotation power of the output shaft <NUM> is reduced to a constant reduction ratio through each the reduction rotation gears 15b and 16b and the reduction output gear <NUM>.

A hydraulic pump <NUM>, which supplies working oil to the forward/reverse rotation switching mechanism <NUM>, is mounted on the end of the reverse rotation shaft <NUM>, which is opposed to the flywheel <NUM> across the reverse rotation clutch <NUM>. The hydraulic pump <NUM> is configured to be driven by rotation of the reverse rotation shaft <NUM> based on rotation power of the engine <NUM>. Therefore, the hydraulic pump <NUM> is driven as long as the engine <NUM> is running, In an embodiment, the hydraulic pump <NUM> is mounted on an upper portion of a rear side of the housing <NUM>.

When the forward/reverse rotation lever <NUM> in the cabin <NUM> is operated in forward/reverse rotation or in neutral, a supply destination of the hydraulic oil is switched to either the forward rotation clutch <NUM>, the reverse rotation clutch <NUM> or the neutral. By pressurizingly contacting friction plates of each of clutches <NUM> and <NUM> by pressure of working oil suitable for clutch engagement, the input shaft <NUM> is connected to the output shaft <NUM> so that power can be transmitted. Namely, when the forward rotation clutch <NUM> is connected and the reverse rotation clutch <NUM> is disconnected, it comes into an advance state where rotation power of the input shaft <NUM> is transmitted as power in the forward rotation (advance) direction to the output shaft <NUM>.

Conversely, when the forward rotation clutch <NUM> is disconnected and the reverse rotation clutch <NUM> is connected, it comes into an retreat state where rotation power of the input shaft <NUM> is transmitted as power in the reverse rotation (retreat) direction to the output shaft <NUM>. When both the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> are disconnected, it becomes a neutral state in which rotation power of the input shaft <NUM> is not transmitted to the output shaft <NUM>. When a slip engagement (half clutch engagement) is attained by increasing or decreasing a degree of pressurizing contact of the friction plates of each of clutches <NUM> and <NUM> with pressure of working oil, a portion of rotation power of the input shaft <NUM> is transmitted to the output shaft <NUM>, so it comes to a low speed propulsion state where the output shaft <NUM> and thus the propeller <NUM> rotate at a low speed. During normal propulsion, adjustment of the propulsion speed of the fishing boat <NUM> is made by means of the throttle lever <NUM> inside the cabin <NUM>.

Next, the structure of the hydraulic circuit <NUM> of the reduction reverse gear <NUM> will be described below with reference to <FIG> in addition to the above referred drawings. The hydraulic circuit <NUM> of the reduction reverse gear <NUM> is provided with the hydraulic pump <NUM> driven by rotational power of the engine <NUM>. The hydraulic pump <NUM> supplies hydraulic oil to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM>, etc. A suction side of the hydraulic pump <NUM> is connected to a working oil tank via a strainer <NUM>. In the embodiment, working oil is stored in the housing <NUM> of the reduction reverse gear <NUM>, and the housing <NUM> functions as the working oil tank.

A working oil path <NUM> led from a discharge side of the hydraulic pump <NUM> is connected to a forward rotation oil path <NUM> which is directed to the forward rotation clutch <NUM> and to a reverse rotation oil path <NUM> which is directed to the reverse rotation clutch <NUM> via a pressure reducing valve <NUM> of a trolling device <NUM> and a forward/reverse rotation switching valve <NUM>. The forward/reverse rotation switching valve <NUM> is of a three-position switching type including a forward rotation position F, a neutral position N, and a reverse rotation position R and is configured to control the forward/reverse rotation switching mechanism <NUM>. Namely, the forward/reverse rotation switching valve <NUM> is configured so that through switching operation of the forward/reverse rotation lever <NUM> as a forward/reverse operation component, it can switch positions among three including the forward rotation position F to supply working oil to the forward rotation clutch <NUM>, the reverse rotation position R to supply working oil to the reverse rotation clutch <NUM>, and the neutral position to stop supplying working oil to both of the clutches <NUM> and <NUM>.

From between the hydraulic pump <NUM> and the forward/reverse rotation switching valve <NUM> in the working oil path <NUM>, a lubricant oil path <NUM> leads to deliver working oil as lubricant oil to each of the clutches <NUM> and <NUM>. There are provided in the lubricant oil path <NUM> a working oil pressure regulating valve <NUM> of being a relief valve for maintaining oil pressure and a lubricant oil pressure regulating valve <NUM>. After passing through the working oil pressure regulating valve <NUM>, the working oil is depressurized by the lubricant oil pressure regulating valve <NUM> and then is delivered as lubricant oil to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM>. Unnecessary working oil (lubricant oil) exceeding a predetermined pressure is returned from the lubricant oil pressure regulating valve <NUM> into the housing <NUM>.

The working oil pressure regulating valve <NUM> is provided with a loose-fitted valve <NUM> which is used to mitigate shock caused by clutch connection operation when switching between the forward rotation and the reverse rotation. The loose-fitted valve <NUM> gradually increase pressure of working oil delivered to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> by back pressure introduced with the forward/reverse rotation switching valve <NUM> to mitigate shock caused by clutch connection operation when switching between the forward rotation and the reverse rotation.

When the forward/reverse rotation switching valve <NUM> is in the neutral position N, a back chamber of the loose-fitted valve <NUM> is drained. The working oil pressure regulating valve <NUM> is opened in a low pressure setting state without being compressed by a relief spring <NUM>. When the forward/reverse rotation switching valve <NUM> is operated to switch it to the forward rotation position F or the reverse rotation position R, working oil slowly flows into the loose-fitted valve <NUM> via the forward/reverse rotation switching valve <NUM>, and the loose-fitted valve <NUM> gradually compresses the relief spring <NUM>. The working oil pressure regulating valve <NUM> then gradually increasingly shifts to a high pressure setting state to reach the predetermined pressure of working oil. This causes pressure of working oil of the forward rotation clutch <NUM> or the reverse rotation clutch <NUM> to gradually increase, and brings the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> to a gradually connected (engaged) state and eventually to a fully fitted state. As a result, shock caused by connecting each of clutches <NUM> and <NUM> can be mitigated.

In the working oil path <NUM> between the hydraulic pump <NUM> and the forward/reverse rotation switching valve <NUM>, not only the lubricant oil path <NUM> but also a pilot oil path <NUM> is branched off. There are provided in the pilot oil path <NUM> a proportional solenoid valve <NUM> to control output oil pressure of the pressure reducing valve <NUM> capable of reducing pressure of working oil and supplying it to the forward/reverse rotation switching mechanism <NUM> and a direct connection solenoid valve <NUM> to turn working oil supply to the proportional solenoid valve <NUM> on or off. The direct connection solenoid valve <NUM> is configured to be able to switch between two positions which are a pressure reducing position to supply pilot pressure to the pressure reducing valve <NUM> and a direct connection position not to supply pilot pressure to the pressure reducing valve <NUM> by excitation or demagnetization of an electromagnetic solenoid in response to a turning on or off state of the trolling switch <NUM>. The proportional solenoid valve <NUM> is duty-controlled according to an operation amount of a trolling dial <NUM>.

When the direct connection solenoid valve <NUM> is activated to be switched to the pressure reducing position by excitation of the electromagnetic solenoid of the direct connection solenoid valve <NUM> in response to the ON operation of the trolling switch <NUM>, the proportional solenoid valve <NUM> whose degree of open is adjusted in accordance with the operation amount of the trolling dial <NUM> applies pilot pressure to the pressure reducing valve <NUM> and causes an internal spool of the pressure reducing valve <NUM> to move slidely. Pressure of the working oil from the working oil path <NUM> is reduced according to the amount of slide movement of the internal spool of the pressure reducing valve <NUM>, and the pressurereduced working oil is supplied to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> via the forward/reverse rotation switching valve <NUM>.

When the direct connection solenoid valve <NUM> is activated to be switched to the direct connection position by demagnetization of the electromagnetic solenoid of the direct connection solenoid valve <NUM> in response to the OFF operation of the trolling switch <NUM>, the proportional solenoid valve <NUM> no longer applies pilot pressure to the pressure reducing valve <NUM>. The internal spool is slidely moved by spring force, so that the pressure reducing valve <NUM> is fully opened. As a result, pressure of working oil from the working oil path <NUM> is not reduced and the working oil is supplied to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> via the forward/reverse rotation switching valve <NUM>. By combining the pressure reducing valve <NUM>, a direct connection solenoid valve <NUM>, and a proportional solenoid valve <NUM>, the trolling device <NUM>, which adjusts pressure of working oil flowing toward the forward/reverse rotation switching mechanism <NUM>, is configured.

<FIG> shows a functional block diagram of a controller <NUM> mounted on the fishing boat <NUM> according to the embodiment. The controller <NUM> mainly supervises control of an overall operation of the engine <NUM> and the reduction reverse gear <NUM>, although the details are omitted in the drawings, it includes a CPU carrying out various arithmetic processes and controls, a ROM for storing control programs and data, a RAM for temporarily storing control programs and data, and an input/output interface, etc..

There are electrically connected to the controller <NUM> a neutral switch <NUM> as an operation detection member to detect the operating position of the forward/reverse rotation lever <NUM>, a throttle potentiometer <NUM> to detect the operating position of the throttle lever <NUM>, a trolling potentiometer <NUM> to detect the operating position of the trolling switch <NUM> and the operating position of the trolling dial <NUM>, two output shaft rotation sensors 47a and 47b to detect the rotation speed of the output shaft <NUM> and thus the propeller <NUM>, an engine rotation sensor <NUM> to detect a rotation speed of the engine <NUM>, the direct connection solenoid valve <NUM> (electromagnetic solenoid thereof), and the proportional solenoid valve <NUM> (electromagnetic solenoid thereof), etc..

In this way, by providing with two output shaft rotation sensors 47a and 47b, the output shaft <NUM> and thus not only the speed of rotation but also the direction of rotation of the propeller <NUM> can be detected, this makes it possible to carry out control suitable for the direction of rotation of the propeller. For example, at the clutch connection control described below, the clutch connection delay can be suppressed when the fishing boat <NUM> is going in a direction opposite to the operation position of the forward/reverse rotation lever <NUM>.

The controller <NUM> controls the direct connection solenoid valve <NUM> and the proportional solenoid valve <NUM> according to the turning on or off state of the trolling switch <NUM> and the operation amount of the trolling dial <NUM>. The neutral switch <NUM> according to the embodiment detects from the operating position of the forward/reverse rotation lever <NUM> whether the forward/reverse rotation switching valve <NUM> is in the neutral position or not. However, the operation detection member is not limited thereto. It may be a device capable of detecting whether the forward/reverse rotation switching valve <NUM> is in the forward rotation position F or the reverse rotation position R, or may be a forward/reverse rotation potentiometer.

According to an embodiment, which is not part of the claimed invention, the controller <NUM> is configured so that in case where the neutral switch <NUM> detects that the forward/reverse rotation switching valve <NUM> is in the neutral position N during normal propulsion (the neutral switch <NUM> is the ON state), the trolling device <NUM> does not reduce pressure of the working oil flowing toward the forward/reverse rotation switching mechanism <NUM>. In other words, the controller <NUM> is configured so that the trolling device <NUM> does not reduce pressure of working oil flowing toward the forward/reverse rotation switching mechanism <NUM> regardless of detection information of the neutral switch <NUM> during normal propulsion. In the embodiment, during normal propulsion in which the trolling switch <NUM> is OFF, regardless of whether the neutral switch <NUM> is on or off, the direct connection solenoid valve <NUM> turns off working oil delivery to the proportional solenoid valve <NUM>, and the pressure reducing valve <NUM> deliveries working oil to the forward/reverse rotation switching mechanism <NUM> without reducing pressure of working oil (see <FIG>).

Thus, even if it is erroneously detected that the neutral switch <NUM> is in the neutral position N, nevertheless the forward/reverse rotation switching valve <NUM> is in a position (F or R) other than the neutral position, working oil with unreduced pressure (high pressure) can be supplied to the forward/reverse rotation switching mechanism <NUM>, thereby preventing the forward/reverse rotation switching mechanism <NUM> from being switched to a power shutdown state. Therefore, it becomes to be not concerned that the forward/reverse rotation switching mechanism <NUM> makes a slip engagement (half-clutch engagement) during normal propulsion within a high-speed rotation range, thereby keeping the forward/reverse rotation switching mechanism <NUM> from problems such as damage or seizure.

Furthermore, as shown in <FIG>, since during low speed propulsion (trolling propulsion) in which the trolling switch <NUM> is ON, regardless of whether the neutral switch <NUM> is on or off, the direct connection solenoid valve <NUM> turns on working oil delivery to the proportional solenoid valve <NUM>, and the pressure reducing valve <NUM> deliveries working oil with reduced pressure to the forward/reverse rotation switching mechanism <NUM> via the forward/reverse rotation switching valve <NUM>, this makes it possible to prevent from shock caused when a sudden increase in pressure of working oil brings the forward/reverse rotation switching mechanism <NUM> into a fully fitted state, as well as to eliminate a problem of sudden acceleration of a propulsion speed during towing for a net hoist.

During normal propulsion, the reduction reverse gear <NUM> according to the embodiment uses not only the loose-fitted valve <NUM> but also the trolling device <NUM> to optimize a control of the clutch connection when switching between the forward rotation and the reverse rotation. In this case, when the forward/reverse rotation lever <NUM> is operated to be switched to a forward rotation direction or a reverse rotation direction, the direct connection solenoid valve <NUM> is activated to be switched to the reduced pressure position by excitation of the electromagnetic solenoid of the direct connection solenoid valve <NUM> in response to the switching operation, and after a transition time TF1 (TR1) elapses, during a relay time TF2 (TR2) the proportional solenoid valve <NUM> applies pilot pressure to the pressure reducing valve <NUM>, and the pressure reduced working oil is delivered to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> via the forward/reverse rotation switching valve <NUM>. Then, during a transition time TF3 (TR3), by gradually decreasing a load of pilot pressure to cause pressure of working oil flowing into the forward rotation clutch <NUM> or the reverse rotation clutch <NUM> to gradually increase and eventually bring the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> to a fully fitted state, and the direct connection solenoid valve <NUM> is activated to be switched to the direct connection position by demagnetization of the electromagnetic solenoid of the direct connection solenoid valve <NUM> (see <FIG> and <FIG>).

In particular, in the embodiment, as shown in <FIG> and <FIG>, an operation pattern of the proportional solenoid valve <NUM> (also referred to as a current value pattern transmitted to the electromagnetic solenoid of the proportional solenoid valve <NUM>) is controlled such that it becomes to be different between when the forward/reverse rotation lever <NUM> is operated to be switched to the forward direction and when it is operated to be switched to the reverse direction. Namely, when the forward/reverse rotation switching valve <NUM> is switched to the forward rotation position F or the reverse rotation position R during normal propulsion, a pattern in which the trolling device <NUM> reduces pressure of working oil flowing toward the forward/reverse rotation switching mechanism <NUM> is controlled such that it becomes to be different between when the forward/reverse rotation switching valve <NUM> is switched to the forward rotation position F and when it is switched to the reverse rotation position R. In the examples shown in <FIG> and <FIG>, transition times are set such that the transition time TR1 when the forward/reverse rotation lever <NUM> is operated in the reverse direction is shorter than the transition time TF1 when it is operated in the forward direction, as well as the working current values are set such that the working current values IR1 and IR2 at the reverse rotation are greater than the working current values IF1 and IF2 at the forward rotation. The operation pattern of the proportional solenoid valve <NUM> is not limited to the examples shown in <FIG> and <FIG>, various patterns can be employed.

For example, when the sizes of the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> are different from each other, this makes it easy to set pressure of working oil, working oil supply rate, and the like according to each of the clutches <NUM> and <NUM>. Therefore, it is possible not only to optimize a connection speed of each of the clutches <NUM> and <NUM>, but also to mitigate shock caused by connection of each of clutches <NUM> and <NUM> at the forward/reverse rotation switching. In particular, in the embodiment, since the transition time TR1 at the reverse rotation is set to be shorter than the transition time TF1 at the forward rotation, as well as the working current values IR1 and IR2 at the reverse rotation are set to be greater than the working current values IF1 and IF2 at the forward rotation, it is possible to retreat the fishing boat <NUM> smoothly by connecting the reverse rotation clutch <NUM> swiftly when a resistance is too large to advance.

Furthermore, the reduction reverse gear <NUM> according to the embodiment is configured so that during transition to low speed propulsion a feedback control is performed based on the rotation speed of the propeller <NUM> (rotation speed of the output shaft <NUM> in the embodiment) after the trolling device <NUM> linearly increases pressure of working oil flowing toward the forward/reverse rotation switching mechanism <NUM>.

In this case, the direct connection solenoid valve <NUM> is activated to be switched to the pressure reducing position by excitation of the electromagnetic solenoid of the direct connection solenoid valve <NUM> in response to the ON operation of the trolling switch <NUM>. After the transition time TF1 elapses, during the relay time TF2 the proportional solenoid valve <NUM> applies pilot pressure to the pressure reducing valve <NUM> by transmitting a working current value IF2 to the electromagnetic solenoid of the proportional solenoid valve <NUM>, and the pressure reduced working oil is delivered to the forward rotation clutch <NUM> and the reverse rotation clutch <NUM> via the forward/reverse rotation switching valve <NUM>. Then, the working current value IF of the electromagnetic solenoid in the proportional solenoid valve <NUM>, and thus a load of pilot pressure is gradually linearly reduced, so that pressure of working oil flowing into the forward rotation clutch <NUM> or the reverse rotation clutch <NUM> is linearly increased. When the rotational speed of the output shaft <NUM> reaches a target value, it is switched to the feedback control based on the rotation speed of the output shaft <NUM> to continue the low speed propulsion (see <FIG>).

This allows the propeller <NUM> to reach the target rotation speed without overshooting during transition to low-speed propulsion, thereby eliminating a problem in which a net is floated by sudden increase in speed when traveling at a low speed, for example.

As shown in <FIG>, when linearly increasing the working current value IF of the electromagnetic solenoid of the proportional solenoid valve <NUM>, and thus the load of pilot pressure, even if the rotation speed of the output shaft <NUM> does not reach the target value, it may be configured to be switched to feedback control based on the rotation speed of the output shaft <NUM> after a predetermined time is lapse. Otherwise, as shown in <FIG>, it may be configured to change an inclination of the working current value IF of the electromagnetic solenoid of the proportional solenoid valve <NUM> step by step over time.

<FIG> shows an alternative example of a functional block diagram of the controller <NUM> according to the embodiment. The controller <NUM> according to the alternative example is electrically connected to a trolling priority switch <NUM> as a trolling priority member which operates to fully close the pressure reducing valve <NUM> in an event where an error such as a communication failure occurs during a low speed propulsion. The trolling priority switch <NUM> is configured to work only at low speed propulsion (only when the trolling switch <NUM> is an ON state).

The controller <NUM> is configured so that when the trolling priority switch <NUM> is an OFF state and an error such as a communication failure occurs, the trolling device <NUM> does not reduce pressure of working oil flowing toward the forward/reverse rotation switching mechanism <NUM>. Namely, the controller is configured so that the direct connection solenoid valve <NUM> turns off working oil supply to the proportional solenoid valve <NUM> and the pressure reducing valve <NUM> delivers working oil to the forward/reverse rotation switching mechanism <NUM> without reducing pressure of working oil.

Claim 1:
A reduction reverse gear (<NUM>) for marine vessel comprising
a hydraulic clutch-type forward/reverse rotation switching mechanism (<NUM>),
wherein said forward/reverse rotation switching mechanism (<NUM>) is configured to convert rotation power of a main engine (<NUM>) mounted on a hull (<NUM>) to an output of forward rotation, neutral, or reverse rotation and to transfer the output to a propeller (<NUM>),
wherein neutral represents a state in which no rotation power is transmitted to the output,
a forward/reverse rotation switching valve (<NUM>) which is a three-position switching type including a forward rotation position, a neutral position and a reverse rotation position and is configured to control a switching operation of the forward/reverse rotation switching mechanism (<NUM>), and
a trolling device (<NUM>) configured to regulate and control the pressure of a working oil flowing toward the forward/reverse rotation switching mechanism (<NUM>), wherein the reduction reverse gear (<NUM>) is configured such that:
when the forward/reverse rotation switching valve (<NUM>) is switched to the forward rotation position or the reverse rotation position during normal propulsion,
wherein during normal propulsion the adjustment of the engine speed is made by means of a throttle lever (<NUM>),
the trolling device (<NUM>) is configured to control a pattern that reduces the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism (<NUM>) so that the pattern is different between when the forward/reverse rotation switching valve (<NUM>) is in the forward rotation position and when the forward/reverse rotation switching valve (<NUM>) is in the reverse rotation position; and
the reduction reverse gear (<NUM>) comprises an operation detection member (<NUM>) configured to detect an operation state of the forward/reverse rotation switching valve (<NUM>);
and when the operation detection member (<NUM>) detects that the forward/reverse rotation switching valve (<NUM>) is in the neutral position during normal propulsion,
the trolling device (<NUM>) is configured to control the working oil so that the pressure of the working oil flowing toward the forward/reverse rotation switching mechanism (<NUM>) is not reduced.