Ship hydraulic drive systems

Abstract

To reduce fluctuation in rotational speed of an electric generator in a system that controls the rotational speed of the electric generator by controlling a hydraulic pump and volume of displacement of the hydraulic pump according to variation in engine rotational speed.SOLUTION: A hydraulic drive system (10) of a vessel including: an engine (11) for generating propulsion power for a vessel; a hydraulic pump (14) coupled to an output shaft (13) of the engine (11) and driven by output of the engine (11); a variable volume type hydraulic motor (15) driven by hydraulic pressure supplied from the hydraulic pump (14); and an electric generator (17) for generating power by using rotational force of the hydraulic motor (15). The hydraulic drive system further includes a fly wheel (29) on a rotational shaft (16) for coupling the hydraulic motor (15) with the electric generator (17).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrostatic drive system for a marine vessel. [Background technology]

[0002] There are known ships, mainly medium- and large-sized ships, equipped with a two-stroke engine that rotates a propeller to output power for propelling the ship, and a four-stroke engine that drives a generator to supply electricity for use on board. Because the two-stroke engines used in such ships are more efficient than four-stroke engines, some ships are equipped with a main shaft generator that uses part of the output of the two-stroke engine to generate electricity in order to reduce the ship's fuel consumption.

[0003] For example, Patent Document 1 discloses a power generation device and propulsion device for a ship that includes a first hydraulic pump driven by the ship's engine, a first hydraulic motor connected to a generator, a first hydraulic circuit that connects the first hydraulic pump and the first hydraulic motor, a first hydraulic pump controller that controls the displacement volume of the first hydraulic pump, a first hydraulic motor controller that controls the displacement volume of the first hydraulic motor, and a generator control device that controls the first hydraulic pump controller and the first hydraulic motor controller to control the rotation speed of the first hydraulic motor, and controls the rotation speed of the generator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-112088 Summary of the Invention [Problem to be solved by the invention]

[0005] To use the power generated by the generator on board, it is necessary to adjust the voltage and frequency to match the onboard power system. One possible solution is to convert the generator output from AC to DC, then convert it back to AC, and convert it to the desired voltage and frequency. However, converters that convert AC to DC and back to AC are expensive, which is an obstacle to practical use.

[0006] On the other hand, the power generation device and propulsion device for a ship described in Patent Document 1 controls the rotation speed of the generator by controlling the displacement of the hydraulic pump and hydraulic motor, respectively, and thereby controls the desired generated voltage and frequency. However, even if the displacement of the hydraulic pump and hydraulic motor is controlled in accordance with fluctuations in engine rotation speed, there is a risk that a mismatch will occur between the timing of fluctuations in engine rotation speed and the timing of changes in displacement, making the rotation speed of the generator unstable.

[0007] The present invention has been made in consideration of the above problems, and provides a hydraulic drive system that can reduce fluctuations in the rotation speed of a generator in a system that controls the displacement of a hydraulic pump and a hydraulic motor in response to fluctuations in engine rotation speed, thereby controlling the rotation speed of a generator. [Means for solving the problem]

[0008] According to one aspect of the invention, an engine for generating propulsion for the vessel; a hydraulic pump connected to an output shaft of the engine and driven by the output of the engine; a variable displacement hydraulic motor driven by hydraulic pressure supplied from the hydraulic pump; a generator that generates electricity by utilizing the rotational force of the hydraulic motor; In a hydraulic drive system for a ship, a flywheel is provided on a rotary shaft connecting the hydraulic motor and the generator; A hydraulic drive system for a vessel is provided. [Effects of the Invention]

[0009] As described above, according to the present invention, in a system that controls the rotation speed of a generator by controlling the displacement of a hydraulic pump and a hydraulic motor in response to fluctuations in engine rotation speed, fluctuations in the rotation speed of the generator can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration example of a hydraulic drive system according to an embodiment of the present invention. [Figure 2] 2 is an explanatory diagram showing a configuration example of a double tilt type swash plate type variable displacement pump motor according to the embodiment; FIG. [Figure 3] FIG. 4 is a schematic diagram showing a configuration example of a hydraulic drive system according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0012] <Hydraulic drive system configuration> An example of the configuration of a hydraulic drive system according to an embodiment of the present invention will be described with reference to FIG. 1 is an explanatory diagram that schematically shows the overall configuration of a hydraulic drive system 10. The hydraulic drive system 10 is configured to include an engine 11, a propeller 12, a hydraulic pump 14, a hydraulic motor 15, a main shaft generator 17, a synchronous phase modifier (rotary condenser) 18, and a control device 30.

[0013] The engine 11 is, for example, a two-stroke diesel engine, and is drive-controlled by the control device 30 to rotate the output shaft 13. The engine 11 may be a gasoline engine, a four-stroke engine, or another type of engine, but a two-stroke engine is suitable for use in medium- or large-sized ships because it consumes less fuel.

[0014] A propeller 12 that propels the vessel by rotation is attached to one end of the output shaft 13. The engine 11 rotates the propeller 12 via the output shaft 13 to generate thrust that propels the vessel. Note that the hydraulic drive system 10 of this embodiment uses a fixed-pitch propeller with a fixed blade angle (pitch), which reduces production costs.

[0015] The engine 11 is configured to be able to rotate forward (in the direction of arrow F) and reverse (in the direction of arrow R). When the engine 11 rotates forward, the propeller 12 rotates forward, and the boat is propelled forward. When the engine 11 rotates reverse, the propeller 12 rotates reverse, and the boat is propelled backward.

[0016] The hydraulic pump 14 is connected to the other end of the output shaft 13 and is driven by the output of the engine 11 to discharge hydraulic oil. In this embodiment, the hydraulic pump 14 is a swash plate type variable displacement piston pump driven by the rotational force of the output shaft 13, and is configured to be able to adjust the discharge flow rate from the hydraulic pump 14 relative to the rotation speed of the engine 11 by controlling the tilt amount (displacement volume), which is the tilt of the swash plate. The tilt amount (tilt amount) of the swash plate can be adjusted by an actuator 14a driven by the control device 30. The hydraulic pump 14 may be attached directly to the output shaft 13 or via a gear mechanism.

[0017] The hydraulic motor 15 is driven by hydraulic pressure supplied from the hydraulic pump 14, and rotates a motor shaft (rotating shaft) 16 that connects the hydraulic motor 15 to a main shaft generator 17. The hydraulic motor 15 is a swash plate type variable displacement pump motor that is rotationally driven by hydraulic pressure, and is configured to be able to adjust the rotation speed of the motor shaft 16 relative to the discharge flow rate from the hydraulic pump 14 by controlling the tilt amount (displacement volume), which is the tilt of the swash plate. The tilt amount of the swash plate (tilt amount) can be adjusted by an actuator 15a driven by the control device 30.

[0018] The hydraulic motor 15 is connected to the hydraulic pump 14 via a first oil passage 24 and a second oil passage 25. A first accumulator 26 is connected to the first oil passage 24. A second accumulator 27 is connected to the second oil passage 25.

[0019] In the hydraulic drive system 10 of this embodiment, a pump motor that can function as both a pump and a motor is used as both the hydraulic pump 14 and the hydraulic motor 15. In this case, the hydraulic pump 14 and the hydraulic motor 15 may basically have the same configuration.

[0020] Here, an example of the configuration of a swash plate type variable displacement pump motor used as the hydraulic pump 14 and the hydraulic motor 15 will be briefly described with reference to Fig. 2. Fig. 2 is a cross-sectional view showing an example of a variable displacement pump motor.

[0021] 2 includes a cover 101, a pump housing 102, and a drive shaft 103 journaled by the cover 101 and the pump housing 102. The drive shaft 103 corresponds to the output shaft 13 of the engine 11 in the hydraulic pump 14, and corresponds to the motor shaft 16 in the hydraulic motor 15.

[0022] The cover 101 is provided with a first supply / discharge passage 104 through which hydraulic oil flows that is sucked in when the pump motor 100 functions as a hydraulic pump and through which hydraulic oil flows that is discharged when the pump motor 100 functions as a hydraulic motor. The cover 101 is also provided with a second supply / discharge passage 105 through which hydraulic oil flows that is discharged when the pump motor 100 functions as a hydraulic pump and through which hydraulic oil flows that is introduced when the pump motor 100 functions as a hydraulic motor.

[0023] In both cases where the pump motor 100 functions as the hydraulic pump 14 and the hydraulic motor 15, the first supply / discharge passage 104 communicates with the second oil passage 25. On the other hand, in both cases where the pump motor 100 functions as the hydraulic pump 14 and the hydraulic motor 15, the second supply / discharge passage 105 communicates with the first oil passage 24.

[0024] A cylinder block 106 is connected to the drive shaft 103 and rotates integrally with the drive shaft 103. A port plate 107 is provided at one end of the cylinder block 106, and a swash plate 108 is provided at the other end. The surface at one end of the cylinder block 106 is in sliding contact with the port plate 107. A plurality of cylinders 109 are defined in the cylinder block 106 along the axial direction of the drive shaft 103. A piston 110 is inserted in each cylinder 109 so as to be axially movable, and the cylinders 109 and pistons 110 define a volume chamber 111. The volume chamber 111 can communicate with a first supply / discharge passage 104 and a second supply / discharge passage 105 formed in the cover 101 via hydraulic ports 112, 113 provided in the port plate 107.

[0025] The end of each piston 110 protruding from the cylinder 109 is in sliding contact with the swash plate 108. When the cylinder block 106 rotates together with the drive shaft 103, the piston 110 rotates around the drive shaft 103 while in sliding contact with the swash plate 108. When the swash plate 108 is tilted with respect to a plane perpendicular to the drive shaft 103, this rotation causes the piston 110 to reciprocate within the cylinder 109, expanding and contracting the volume chamber 111.

[0026] When the pump motor 100 is made to function as the hydraulic pump 14, the swash plate 108 is tilted so that the first supply / discharge passage 104 of the cover 101 communicates with the volume chamber 111 in the region where the volume chamber 111 expands, and so that the second supply / discharge passage 105 communicates with the volume chamber 111 in the region where the volume chamber 111 contracts. As a result, as the pump motor 100 rotates, hydraulic oil is drawn into the volume chamber 111 from the second oil passage 25 via the first supply / discharge passage 104, and after being pressurized within the volume chamber 111, it is discharged to the first oil passage 24 via the second supply / discharge passage 105. The discharge flow rate is adjusted by controlling the amount of tilt.

[0027] When the pump motor 100 is made to function as the hydraulic motor 15, the swash plate 108 is tilted so that the first supply / discharge passage 104 communicates with the volume chamber 111 in a region where the volume chamber 111 contracts, and the second supply / discharge passage 105 communicates with the volume chamber 111 in a region where the volume chamber 111 expands. As a result, the pump motor 100 is rotationally driven by the hydraulic pressure discharged from the hydraulic pump 14 via the first oil passage 24, and output torque is generated on the drive shaft 103 (motor shaft 16).

[0028] The inclination (amount of tilt) of the swash plate 108 can be adjusted by an actuator 114. The pump motor 100 shown in FIG. 2 is a double-tilt (over-center) variable displacement pump motor, and the swash plate 108 is configured to be tiltable in both directions. The actuator 114 is configured with a hydraulic circuit equipped with a directional control valve and the like, and can tilt the swash plate 108 in either direction by selectively increasing the pressure of hydraulic oil supplied to one of two pressure chambers. In addition, the amount of tilt can be reduced to zero by supplying hydraulic oil to the two pressure chambers in a predetermined balance. This allows the pump motor 100 to stop functioning as a hydraulic pump or hydraulic motor. The actuator 114 is controlled by the control device 30.

[0029] In the hydraulic drive system 10 of this embodiment, the hydraulic pump 14 functions as a pump that supplies hydraulic oil to the hydraulic motor 15 and rotationally drives the hydraulic motor 15 during a power generation mode in which the output of the engine 11 is used to cause the main shaft generator 17 to generate electricity. During the power generation mode, the tilt amount of the hydraulic pump 14 is controlled by the control device 30 so that the discharge pressure is constant. Furthermore, during an assist mode in which an assist force is applied to the output shaft 13 of the engine 11 by the drive torque output from the main shaft generator 17, the hydraulic pump 14 functions as a motor that is rotationally driven by hydraulic oil supplied from the hydraulic motor 15 and applies rotational torque to the output shaft 13.

[0030] Furthermore, during the power generation mode, the hydraulic motor 15 functions as a motor that is rotationally driven by hydraulic oil supplied from the hydraulic pump 14 to apply rotational torque to the motor shaft 16. During the assist mode, the hydraulic motor 15 functions as a pump that supplies hydraulic oil to the hydraulic pump 14 to rotationally drive the hydraulic pump 14.

[0031] Returning to FIG. 1 , a main shaft generator 17 is connected to the other end of the motor shaft 16 of the hydraulic motor 15. The main shaft generator 17 generates electricity by utilizing the rotational force of the hydraulic motor 15 transmitted via the motor shaft 16. The main shaft generator 17 may be any generator that can generate electricity using a change in magnetic field caused by the rotation of the rotor together with the rotation of the motor shaft 16, and for example, a three-phase AC generator can be used. In this embodiment, the main shaft generator 17 is configured as a generator motor that supplies current to the main shaft generator 17 during the assist mode to cause it to function as a rotating electric machine and rotate the motor shaft 16 to output drive torque.

[0032] The main shaft generator 17 is equipped with a rotational speed detector 28 that detects the rotational speed of the main shaft generator 17. The rotational speed detector 28 may be provided in the hydraulic motor 15 or at any position on the motor shaft 16, as long as it can detect a rotational speed correlated with the rotational speed of the main shaft generator 17.

[0033] During the power generation mode, the tilt amount of the hydraulic motor 15 is adjusted so that the rotation speed of the main shaft generator 17 detected by the rotation speed detector 28 becomes a predetermined target rotation speed, and the power generated by the main shaft generator 17 is controlled to have a voltage and frequency compatible with the ship's power system 20. The swash plate-type variable displacement hydraulic motor 15 can control the rotation speed of the motor shaft 16 steplessly and with fast response by controlling only the swash plate, which has a small mass and inertia mass. If the detected rotation speed is slower than the commanded target rotation speed, the control device 30 drives the actuator 15a to increase the tilt amount of the hydraulic motor 15. If the detected rotation speed is faster than the commanded target rotation speed, the control device 30 drives the actuator 15a to decrease the tilt amount of the hydraulic motor 15.

[0034] A flywheel 29 is attached to the motor shaft 16. The flywheel 29 has the function of stabilizing the rotational speed of the motor shaft 16 by utilizing the inertial force generated when the motor shaft 16 rotates. The hydraulic motor 15 and the main shaft generator 17 may be provided coaxially on the motor shaft 16, or may be provided on a rotating shaft connected to the motor shaft 16 via a gear mechanism. In this case, the flywheel 29 may be provided on either the motor shaft 16 or a predetermined rotating shaft. Similarly, the rotational speed detector 28 may be provided at any position on the predetermined rotating shaft.

[0035] The synchronous phase modifier 18 connects the main shaft generator 17 to the power grid with no load, and adjusts the field current to adjust the voltage supplied to the power grid. A relay switch 19 enables switching between connection and disconnection between the synchronous phase modifier 18 and the ship's power grid 20. One or more auxiliary power generating systems 22a, 22b are also connected to the power grid 20 via relay switches 21a, 21b. Examples of the auxiliary power generating systems 22a, 22b include generators for supplying power used on the ship, fuel cells, etc., but are not limited to these power generating systems.

[0036] During a power generation mode in which power generated by the main shaft generator 17 is supplied to an onboard power system 20, the relay switch 19 connects the synchronous phase modifier 18 to the power system 20. During the power generation mode, the relay switches 21a and 21b connect the power system 20 to at least one of the auxiliary power generation systems 22a and 22b, and the power generated by the main shaft generator 17 may be used onboard together with the power generated by the auxiliary power generation systems 22a and 22b.

[0037] Also, during an assist mode in which the main shaft generator 17 is driven as a rotating electric machine to provide an assist force to the engine 11, the synchronous phase modifier 18 and the power grid 20 are connected by the relay switch 19. During the assist mode, the relay switches 21a, 21b may connect the power grid 20 to at least one of the auxiliary power generating systems 22a, 22b, and electric power generated by the auxiliary power generating systems 22a, 22b may be supplied to the main shaft generator 17.

[0038] The control device 30 includes a processing unit 31 including an arithmetic processing device such as a CPU (Central Processing Unit), and a storage unit 33 including storage memories such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The control device 30 is configured to be able to acquire a signal corresponding to the rotation speed output from the rotation speed detector 28. The control device 30 is also configured to be able to send and receive signals to and from an auxiliary power generation control device 40 that controls the operation of the auxiliary power generation systems 22a, 22b. The storage unit 33 stores computer programs executed by the arithmetic processing device, various parameters and reference data used in calculations by the arithmetic processing device, calculation results, etc.

[0039] The processing unit 31 executes a computer program stored in the storage unit 33 to control the operations of the engine 11, the actuator 14a of the hydraulic pump 14, the actuator 15a of the hydraulic motor 15, the main shaft generator 17, and the synchronous phase modifier 18. The processing unit 31 may be configured to include a plurality of arithmetic processing devices that respectively control the engine 11, the actuators 14a and 15a, the main shaft generator 17, and the synchronous phase modifier 18.

[0040] <Action and effect> Next, the effects of the hydraulic drive system 10 according to this embodiment will be described.

[0041] (Stabilization of generated power when the load on the main generator fluctuates) The load on the main shaft generator 17 fluctuates according to changes in the required power used on board the ship and the amount of power supply generated by the auxiliary power generating systems 22a, 22b. When the load on the main shaft generator 17 increases, the shaft rotation torque that drives the main shaft generator 17 increases, and the rotation speed of the main shaft generator 17 temporarily decreases. Accordingly, the rotation speed of the hydraulic motor 15 connected to the main shaft generator 17 via the motor shaft 16 also decreases, so the control device 30 increases the tilt amount to maintain the rotation speed of the hydraulic motor 15, and outputs the shaft rotation torque required to maintain the rotation speed of the main shaft generator 17 at the target rotation speed.

[0042] At this time, a temporary increase in the required flow rate of hydraulic oil introduced into the hydraulic motor 15 is compensated for by supplying hydraulic oil stored in the first accumulator 26. Furthermore, in this embodiment, the hydraulic pump 14 is also a tilting variable displacement pump, and therefore the steady required flow rate thereafter is maintained by increasing the tilting amount of the hydraulic pump 14 by the control device 30 to increase the discharge flow rate of the hydraulic pump 14.

[0043] On the other hand, when the load on the main shaft generator 17 decreases, the shaft rotation torque that drives the main shaft generator 17 decreases, and the rotation speed of the main shaft generator 17 temporarily increases. Accordingly, the rotation speed of the hydraulic motor 15 connected to the main shaft generator 17 via the motor shaft 16 also increases, so the control device 30 reduces the tilt amount to maintain the rotation speed of the hydraulic motor 15, thereby reducing the output torque, and outputs the shaft rotation torque required to maintain the rotation speed of the main shaft generator 17 at the target rotation speed.

[0044] At this time, the temporary decrease in the required flow rate of hydraulic oil introduced into the hydraulic motor 15 is ensured by storing hydraulic oil in the first accumulator 26. Furthermore, in this embodiment, the hydraulic pump 14 is also a tilting variable displacement pump, so the steady required flow rate thereafter is maintained by reducing the tilting amount of the hydraulic pump 14 by the control device 30 to reduce the discharge flow rate of the hydraulic pump 14.

[0045] In this way, the control device 30 controls the tilt amount of the hydraulic motor 15 in response to fluctuations in the load on the main shaft generator 17 due to changes in the required power on board the ship and the power generated by the auxiliary power generating systems 22a, 22b, thereby attempting to maintain the rotation speed of the main shaft generator 17 at a predetermined target rotation speed. However, because the control device 30 controls the tilt amount of the hydraulic motor 15 in accordance with increases and decreases in the rotation speed of the main shaft generator 17 detected by the rotation speed detector 28, a time lag occurs between when the rotation speed of the main shaft generator 17 changes and when the amount of hydraulic oil supplied to the hydraulic motor 15 increases or decreases.

[0046] On the other hand, in the hydraulic drive system 10 according to this embodiment, a flywheel 29 is attached to the motor shaft 16. The flywheel 29 stores rotational kinetic energy, thereby mitigating fluctuations in the shaft rotation torque required to drive the main shaft generator 17 and making it easier to maintain the rotational speed of the motor shaft 16. In other words, the inertial force generated when the motor shaft 16 rotates can absorb variations in the rotational speed, and even if the load on the main shaft generator 17 fluctuates, the rotational speed of the motor shaft 16 can be stabilized until the amount of hydraulic oil supplied to the hydraulic motor 15 increases or decreases. Therefore, the voltage and frequency of the power generated by the main shaft generator 17 can be stabilized. Furthermore, the power consumption required to stabilize the power generated by the main shaft generator 17 can be reduced.

[0047] (Stabilization of power generated by the main shaft generator when the engine is rotating in reverse) For example, in small vessels, a reversing gear is provided between the engine output shaft and the propeller shaft, and when the vessel is moving backwards, the reversing gear is connected to rotate the propeller in the reverse direction while maintaining the engine rotation direction in a fixed direction. However, providing a reversing gear between the engine and the propeller shaft of a medium-sized or large vessel inevitably increases costs. For this reason, in the hydraulic drive system 10 of this embodiment, the rotation of the engine 11 is switched between forward rotation (F) and reverse rotation (R) depending on the propulsion direction (forward or reverse) of the vessel.

[0048] In this case, if the rotation direction of the main shaft generator 17 is also reversed, the phase rotation of the power generated by the main shaft generator 17 will also be reversed, so measures such as providing a phase reversing disconnector that swaps two of the three phases will be necessary. However, using a phase reversing disconnector increases the number of parts and also leads to an increase in production costs.

[0049] For this reason, in the hydraulic drive system 10, at least one of the hydraulic pump 14 and the hydraulic motor 15 is configured as a bi-directional swash plate variable displacement pump. In the hydraulic drive system 10 of this embodiment, both the hydraulic pump 14 and the hydraulic motor 15 are configured as bi-directional swash plate variable displacement pumps. When the rotation of the engine 11 becomes reverse rotation R when the boat is moving backward, the control device 30 controls the tilt direction of either the hydraulic pump 14 or the hydraulic motor 15 to the opposite direction beyond a state where the tilt amount is zero. As a result, even when the rotation direction of the engine 11 is reversed and the rotation direction of the hydraulic pump 14 is reversed, the rotation direction of the hydraulic motor 15 can be maintained constant.

[0050] 1, when the output shaft 13 of the engine 11 is rotated forward F to move the boat forward, hydraulic oil discharged from the hydraulic pump 14 flows through the first oil passage 24 in the direction of arrow A1 and is supplied to the hydraulic motor 15. Furthermore, hydraulic oil discharged from the hydraulic motor 15 flows through the second oil passage 25 in the direction of arrow A2 and is drawn into the hydraulic pump 14. In this state, the motor shaft 16 rotates in the direction of arrow Fm.

[0051] On the other hand, when the output shaft 13 of the engine 11 is rotated in the reverse direction R to move the boat backward, for example by reversing the tilt direction of the hydraulic pump 14, the hydraulic oil discharged from the hydraulic pump 14 flows through the first oil passage 24 in the direction of arrow A1 and is supplied to the hydraulic motor 15. The hydraulic oil discharged from the hydraulic motor 15 flows through the second oil passage 25 in the direction of arrow A2 and is drawn into the hydraulic pump 14. At this time, the tilt direction of the hydraulic motor 15 remains unchanged, so the rotation direction of the motor shaft 16 is maintained as indicated by arrow Fm.

[0052] Furthermore, when the output shaft 13 of the engine 11 is rotated in the reverse direction R to move the boat backward, for example by reversing the tilt direction of the hydraulic motor 15, the hydraulic oil discharged from the hydraulic pump 14 flows through the second oil passage 25 in the direction of arrow B2 and is supplied to the hydraulic motor 15. The hydraulic oil discharged from the hydraulic motor 15 flows through the first oil passage 24 in the direction of arrow B1 and is sucked into the hydraulic pump 14. At this time, because the tilt direction of the hydraulic motor 15 has been reversed, the rotation direction of the motor shaft 16 is maintained as indicated by arrow Fm.

[0053] Furthermore, even if only one of the hydraulic pump 14 or the hydraulic motor 15 is configured as a double tilting swash plate type variable displacement pump, the rotation direction of the motor shaft 16 can be maintained in a constant direction by reversing the tilting direction of the hydraulic pump 14 or the hydraulic motor 15 when the engine 11 is rotated in reverse R as described above.

[0054] As described above, the hydraulic drive system 10 of this embodiment uses a bi-directional swash plate variable displacement pump for at least one of the hydraulic pump 14 and the hydraulic motor 15, and is therefore able to maintain the rotation direction of the motor shaft 16 in a constant direction regardless of the rotation direction of the engine 11 without using additional parts such as a phase reversing disconnector. This makes it possible to reduce the number of parts and suppress increases in production costs.

[0055] <Modification> So far, the hydraulic drive system 10 according to this embodiment has been described, but various modifications are possible to the hydraulic drive system 10 of the above embodiment. Some modifications of the hydraulic drive system 10 will be described below.

[0056] (Example of a fixed displacement hydraulic pump) In the above embodiment, both the hydraulic pump 14 and the hydraulic motor 15 are variable displacement pumps, but the hydraulic pump may also be a fixed displacement pump. If the hydraulic pump 14 is a fixed displacement pump, when the load on the main shaft generator 17 increases, the control device 30 outputs a command signal to the auxiliary power generation control device 40 to increase the amount of power generated by the auxiliary power generation systems 22a, 22b. Also, if the hydraulic pump 14 is a fixed displacement pump, when the load on the main shaft generator 17 decreases, the control device 30 outputs a command signal to the auxiliary power generation control device 40 to decrease the amount of power generated by the auxiliary power generation systems 22a, 22b.

[0057] This suppresses fluctuations in the load on the main shaft generator 17, maintaining the load on the main shaft generator 17. Even in this case, the rotation speed of the motor shaft 16 may fluctuate due to a time lag between when the amount of power generated by the auxiliary power generating systems 22a and 22b increases or decreases. However, by attaching the flywheel 29 to the motor shaft 16, the rotation speed of the motor shaft 16 can be stabilized.

[0058] Even when the hydraulic pump 14 is a fixed displacement pump, if the hydraulic motor 15 is a double tilting swash plate type variable displacement pump, the rotation direction of the motor shaft 16 can be maintained in a constant direction even when the rotation direction of the engine 11 is reversed as described above.

[0059] (Example of a combination of a variable displacement pump and a fixed displacement pump) In the above embodiment, both the hydraulic pump 14 and the hydraulic motor 15 are variable displacement pumps, but the hydraulic pump may be a combination of a fixed displacement pump and a variable displacement pump.

[0060] In the hydraulic drive system 50 shown in Fig. 3, a fixed displacement hydraulic pump 55 is connected to the output shaft 13 of the engine 11. A first gear 51 is fixed to the output shaft 13, and a second gear 52 is provided which meshes with the first gear 51. A variable displacement pump 54 is connected to a rotary shaft 53 of the second gear 52. A third oil passage 56 connected to the first oil passage 24 and a fourth oil passage 57 connected to the second oil passage 25 are connected to the variable displacement pump 54.

[0061] In this hydraulic drive system 50, a fixed displacement hydraulic pump 55 is used, for example, a pump with a capacity that can realize a rotation speed of the motor shaft 16 that generates an amount of power equivalent to a predetermined reference amount of power required on board the ship by the main shaft generator 17. In addition, in the variable displacement pump 54, the actuator 54a is operated by the control device 30 during the power generation mode so that the pressure (discharge pressure) of the hydraulic oil supplied to the hydraulic motor 15 is kept constant.

[0062] Even with the hydraulic drive system 50 configured in this manner, it is possible to obtain the effect of stabilizing the generated power when the load on the main shaft generator 17 fluctuates, and stabilizing the generated power of the main shaft generator when the engine is rotating in reverse. Furthermore, the hydraulic drive system 50 can reduce the capacity of the variable displacement pump 54 that keeps the pressure (discharge pressure) of the hydraulic oil supplied to the hydraulic motor 15 constant, and can reduce the cost of the variable displacement pump 54.

[0063] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0064] 10: hydraulic drive system, 11: engine, 12: propeller, 13: output shaft, 14: hydraulic pump, 14a: actuator, 15: hydraulic motor, 15a: actuator, 16: motor shaft (rotating shaft), 17: main shaft generator, 18: synchronous phase modifier, 20: power system, 22a and 22b: auxiliary power generation system, 24: first oil line, 25: second oil line, 26: first accumulator, 27: second accumulator, 28: rotational speed detector, 29: flywheel, 30: control device, 40: auxiliary power generation control device

Claims

1. an engine (11) for generating a propulsive force for the vessel; a hydraulic pump (14) connected to an output shaft (13) of the engine (11) and driven by the output of the engine (11); a variable displacement hydraulic motor (15) driven by hydraulic pressure supplied from the hydraulic pump (14); a generator (17) that generates electricity by utilizing the rotational force of the hydraulic motor (15); A hydraulic drive system (10) for a vessel, comprising: At least one of the hydraulic pump (14) and the hydraulic motor (15) has a double tilt variable displacement configuration, a flywheel (29) is provided on a rotating shaft (16) connecting the hydraulic motor (15) and the generator (17); A hydraulic drive system for a vessel, comprising:

2. The hydraulic motor (15) is a swash plate type hydraulic motor, A control device (30) that controls the hydraulic motor (15) The tilt amount of the hydraulic motor (15) is controlled so that the rotation speed of the generator (17) becomes a predetermined target rotation speed.

2. A hydraulic drive system for a vessel according to claim 1.

3. and an accumulator (26, 27) connected to a hydraulic circuit (24, 25) connecting the hydraulic pump (14) and the hydraulic motor (15).

3. A hydraulic drive system for a vessel according to claim 1 or 2.

4. A control device (30) for controlling the double tilt variable displacement hydraulic pump (14) or the hydraulic motor (15) includes: The tilt direction of the hydraulic pump (14) or the hydraulic motor (15) is reversed to maintain the rotation direction of the generator (17) in a constant direction regardless of whether the output shaft (13) of the engine (11) is rotating in a forward direction (F) or a reverse direction (R).

2. A hydraulic drive system for a vessel according to claim 1.

5. The hydrolic drive system (10) of the vessel comprises: The vehicle is configured to be switchable between a power generation mode in which the generator (17) generates electricity using the output of the engine (11) and an assist mode in which the generator (17) outputs a driving torque to assist the output of the engine (11), In the assist mode, The generator (17) is driven by a supply current to output a driving torque; The hydraulic motor (15) is driven by the driving torque to supply hydraulic pressure to the hydraulic pump (14); The hydraulic pump (14) is driven by the hydraulic pressure and applies an assist force to the output shaft of the engine (11).

2. A hydraulic drive system for a vessel according to claim 1.

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