EP4650265A1

EP4650265A1 - Method to engage an input clutch of a marine hybrid drive unit and marine hybrid drive unit

Info

Publication number: EP4650265A1
Application number: EP24176056.0A
Authority: EP
Inventors: Fernando Gallato; Mattia Caracristi; Michele Zottele
Original assignee: ZF Friedrichshafen AG; ZF Padova SRL
Current assignee: ZF Friedrichshafen AG; ZF Padova SRL
Priority date: 2024-05-15
Filing date: 2024-05-15
Publication date: 2025-11-19

Abstract

The present invention relates to a method to engage a pressure operated input clutch (5) of a marine hybrid drive unit (100) to connect a combustion engine (1) with a transmission input shaft (4) of the hybrid drive unit (100). The marine hybrid drive unit (100) comprising the combustion engine (1), an electric drive motor (2) and a transmission (3). The combustion engine (1) comprising an electric start motor (8). The electric drive motor (2) is permanently connected to the transmission input shaft (4). The transmission input shaft (4) can be driven in a combustion engine mode solely by the combustion engine (1), in an electric propulsion mode solely by the electric drive motor (2) and in a combined mode by the combustion engine (1) and the electric drive motor (2). A pressure for actuating the input clutch (5) is provided by an oil pump (6) which is driven by the transmission input shaft (4). The method comprising the steps:
a) starting the combustion engine (1) by the electric start motor (8) and starting the electric drive motor (2),
b) adjusting the rotation speed of the electric drive motor (2) to drive the oil pump (6) with a speed which is sufficient to provide enough pressure to engage the input clutch (5),
c) engaging the input clutch (5).

Further proposed is a marine hybrid drive unit (100) comprising a control unit (101), which is configured to execute said method.

Description

The present invention relates to a method to engage an input clutch of a marine hybrid drive unit in a water vessel.
There is an increasing demand for marine hybrid drive units for environmental and efficiency reasons. With a marine hybrid drive unit a water vessel can be propelled solely by an electric drive motor without any local emissions especially in ecologically sensitive areas or in harbors and mooring areas. During certain operating phases it is also more efficient to propel a water vessel solely by the electric drive motor, for example if a water vessel shall be propelled with low speed in a trolling mode or in a no-wake area. Whereas the combustion engine provides sufficient power for normal and high-speed cruising.
Different marine hybrid drive units comprising a combustion engine and an electric drive motor to propel a water vehicle are already known from prior art. One example of a marine drive hybrid drive unit has been disclosed in US 2009/0209146 A1 . This document describes a hybrid module for installation between an internal combustion engine and a transmission of a water vessel. The combustion engine and an electric drive motor of the hybrid module may be selectively used to propel a water vessel. Different embodiments of such a hybrid module and different start and driving modes are disclosed with this document. One embodiment is described with a separate starter unit which is used to start the combustion engine. Another embodiment with positive locking clutches is described in US 2009/0209146 A1 , wherein the combustion engine can be started by an electric drive motor of the hybrid module.
The purpose of the present invention is to provide an improved method to engage an input clutch of a marine hybrid drive unit and a marine hybrid drive unit comprising a control unit, which is arranged to implement such a method.
This purpose is achieved by a method according to claim 1 and a marine hybrid drive unit according to claim 5. Further embodiments are claimed in dependent claims.
The present invention provides a method to engage a pressure operated input clutch of a marine hybrid drive unit, wherein the pressure operated input clutch connects a combustion engine with a transmission input shaft of the marine hybrid drive unit. The marine hybrid drive unit comprising the combustion engine, an electric drive motor and a transmission. The combustion engine itself comprising an electric start motor. A crank shaft of the combustion engine can be connected to an input element of the input clutch via a module input shaft, i.e. the input shaft of a hybrid module. This means, that an existing conventional marine drive unit without an electric drive motor can be modified to a marine hybrid drive unit by a hybrid module comprising the electric drive motor without modifying the combustion engine. Said hybrid module may include its own module housing to enclose at least some components of the electric drive train. The electric drive motor can either be enclosed in said module housing or it can be located outside the housing.
The electric drive motor can be part of the hybrid module which is mounted between the combustion engine and the transmission. The electric drive motor is permanently connected to the transmission input shaft. The transmission comprises a transmission housing and transmission elements which are arranged in the transmission housing to transfer the rotational speed and power of the transmission input shaft to a required speed of an output shaft which is connected to a propeller shaft of the water vessel. Further transmission elements like one or more clutches can be arranged in the transmission housing to connect or disconnect the input shaft from the output shaft and/or to change the direction of rotation between the input shaft and the output shaft.
Said transmission input shaft of the marine hybrid drive unit can be driven in different modes. In a combustion engine mode the transmission input shaft may be driven solely by the combustion engine. In an electric propulsion mode the transmission input shaft may solely be driven by the electric drive motor. In this electric propulsion mode the water vessel can be propelled at zero noise and zero emissions, especially during low-speed cruising and docking. In a combined mode the transmission input shaft may be driven by the combustion engine and the electric drive motor simultaneously. The electric drive motor is permanently connected to the transmission input shaft. This way, the electric drive motor can be used as a generator to recharge the batteries, while the transmission input shaft is driven by the combustion engine in the combustion engine mode. In a pure recharge mode the combustion engine drives the electric drive motor via the transmission input shaft when the input clutch is engaged and while an output shaft of the transmission in disconnected from the transmission input shaft. In the recharge mode electric energy can be generated without driving the propeller.
A pressure for actuating the input clutch is provided by an oil pump which is driven by the transmission input shaft. This means, that there will be enough oil pressure to actuate the input clutch, whenever the transmission input shaft is rotating with a minimum rotation speed. The oil pump can be an integral part of the transmission.
The proposed method comprises the following steps:

a) starting the combustion engine by the electric start motor and starting the electric drive motor,
b) adjusting the rotation speed of the electric drive motor to drive the oil pump with a speed which is sufficient to provide enough pressure for engaging the input clutch, and
c) engaging the input clutch.

Regarding step a), the combustion engine and the electric drive motor can be started in either order. This means, that either the combustion engine is started before the electric drive motor or vice versa. This method allows the activation of the pressure actuated input clutch without any additional oil pump in the marine hybrid drive unit. The one oil pump which is driven by the input shaft can be a conventional oil pump which is required anyway for the lubrication of transmission components and for providing pressure for pressure actuated transmission clutches inside the transmission. This oil pump can be a gear type oil pump, as an example.
The rotation speed of the electric drive motor can be adjusted to synchronize a rotation speed of the transmission input shaft with an engine speed of the combustion engine before engaging the input clutch. This synchronization can be executed by means of an electronic control unit. The synchronization does not need to synchronize said two rotation speeds to exactly the same rotation speed. In many cases it can be sufficient, to synchronize the rotation speed of the transmission input shaft with the engine speed to reach a limited range of a rotation speed difference. For this purpose a threshold value for a maximum rotation speed difference can be preset in a control unit, wherein the input clutch can be engaged as soon as the preset threshold value of a rotation speed difference is reached.
Said synchronization of the rotation speeds helps to avoid detrimental torque peaks that could occur during the engagement of the input clutch. Such torque peaks could be caused by different rotation speeds between the input element and the output element of the input clutch. The cause of the possible torque peaks is the amount of inertia of the masses connected to the output element of the input clutch. These masses are the masses of the gears of the hybrid module, the rotational parts of the electric drive motor, the transmission input shaft, and the input parts of a transmission clutch. Said synchronizing of the rotation speeds allows the use of an input clutch in form of a form fitting clutch, for example a dog clutch, instead of a friction clutch.
In a further step the marine hybrid drive unit can be switched in the combustion engine mode and the electric drive motor can be switched to a generator mode after the combustion engine has reached a preset engine speed. Preferably the preset engine speed is set to a value in a range between 600 rpm and 800 rpm. The preset engine speed can be the idling speed of the corresponding combustion engine, which is also appropriate to drive the electric drive motor in the recharge mode.
The invention includes a marine hybrid drive unit comprising a control unit, which is configured to execute a method as described above.
There can be mounted at least one gear step between the electric drive motor and the transmission input shaft to achieve an appropriate gear ratio between high rotation speed of an electric drive motor shaft and relatively lower rotation speeds of the transmission input shaft. The gear ratio of the at least one gear step can be optimized to build up an appropriate oil flow rate and oil pressure provided by the oil pump. Other targets of the optimized gear ratio are to maximize the efficiency of the electric drive motor either in the electric propulsion mode or in the recharge mode. For that purposes the gear ratio of the at least one gear step preferably is set to a value in the range between 2 and 3.
The pressure actuated input clutch preferably comprises an input element and an output element, wherein the input element is connected to the module input shaft, and wherein the output element is connected to the transmission input shaft. The pressure actuated input clutch can be a friction clutch with at least one friction disk at the input side and the output side. The input element and the output element in such a friction clutch can be a friction disk carrier.
In this embodiment, the mentioned oil pump can be an integral part of the transmission, wherein the oil pump is driven the transmission input shaft. Transmission elements are arranged in the transmission to transfer the rotational speed of the input shaft to a required speed of an output shaft which is connected to a propeller shaft of the water vessel. Further transmission elements like one or more clutches can be arranged in the transmission to connect or disconnect the input shaft from the output shaft and/or to change the direction of rotation between the input shaft and the output shaft.
In one embodiment the control unit is further configured to execute a backup-method to start the combustion engine in case of a failure of the electric start motor. Said backup-method comprising the following steps:

a) starting the electric drive motor,
b) adjusting the rotation speed of the electric drive motor to drive the oil pump with a speed which is sufficient to provide enough pressure to engage the input clutch,
c) engaging the input clutch and
d) starting the combustion engine by means of the electric drive motor.

Such a backup-method increases the reliability of the marine hybrid drive unit and allows the start of the combustion engine in case of a failure of the electric start motor of the combustion engine. Such a failure can be caused by a defective electric start motor itself or by a low charge level of a corresponding battery.
The invention will be further and more particularly described in the following, by way of example only, and with reference to the accompanying figures.

Fig. 1: shows a first embodiment of a marine hybrid drive unit according to the invention in a schematic drawing and
Fig. 2: shows a scheme of the steps of a method according to the invention.

A marine hybrid drive unit 100 as shown in Fig. 1 can be mounted inside the hull of a water vessel. The marine hybrid drive unit 100 comprises a combustion engine 1 and an electric drive motor 2 for propelling the water vessel in different operation modes. The marine hybrid drive unit 100 can be driven in a combustion engine mode solely by the combustion engine 1, in an electric propulsion mode solely by the electric drive motor 2. In a combined mode the marine hybrid drive unit 100 can be driven simultaneously by the combustion engine 1 and the electric drive motor 2. In a recharge mode the electric drive motor 2 can be driven by the combustion engine 1, when the input clutch 5 is engaged and the transmission clutch 15 is disengaged.
The combustion engine 1 includes an electric start motor 8 and a crankshaft 9. The crankshaft 9 can be connected to a transmission input shaft 4 by means of a pressure actuated input clutch 5. The crankshaft 9 and the transmission input shaft 4 are arranged coaxial to each other. The crankshaft 9 is permanently connected to an input element 12 of the input clutch 5 via a module input shaft 21. The transmission input shaft 4 is fastened to an output element 13 of the input clutch 5.
The input clutch 5 in this embodiment is a multi-disk-friction-clutch with inner and outer friction disks. The input element 12 being designed as an inner disk carrier, whereas the output element 13 is designed as an outer disk carrier. The input clutch 5 is configured to be pressure actuated by means of an appropriate oil supply system. The oil pressure in said oil supply system is provided by an oil pump 6.
The oil pump 6 is provided to supply sufficient oil pressure for actuating the input clutch 5 and a transmission clutch 15 inside the transmission housing 14. The oil pump 6 is driven by the transmission input shaft 4. The transmission clutch 15 is configured to control the speed of an output shaft 16 of the transmission 3. The transmission clutch 15 is a hydraulically actuated multi-disc clutch. The transmission clutch 15 can be fully engaged, fully disengaged or it can be operated in a slipping mode for propelling the water vessel with low speed. In the slipping mode a slip rate of the transmission clutch 15 can be adjusted by controlling the oil pressure in the hydraulic actuation system of the transmission clutch 15.
The input clutch 5 and the electric drive motor 2 are part of a hybrid module 20 which is mounted in between the combustion engine 1 and a transmission 3. The electric drive motor 2 is mounted to a module housing 11 of the hybrid module 20 such, that a motor shaft 10 of the electric drive motor 2 is arranged in parallel to the transmission input shaft 4. The electric drive motor 2 is permanently connected to the transmission input shaft 4 and to the output element 13 of the input clutch 5.
The hybrid module 20 further includes gear steps 7 between the electric drive motor 2 and the transmission input shaft 4. The gear steps 7 in this embodiment comprises a first spur gear 17 which is fastened to the motor shaft 10. The first spur gear 17 meshes with a second spur gear 18. The second spur gear 18 further meshes with a toothing 19 which is an integral part of the output element 13 of the input clutch 5. The gear steps 7 are designed to provide a transmission ratio in the range between 2 and 3, as this has proven to be the optimum range in view of the efficiency of the electric drive motor 2 in the electric propulsion mode and in the recharge mode. The pressure actuated input clutch 5 is also a part of the hybrid module 20.
A control unit 101 of the marine hybrid drive unit 100 is configured to execute the proposed method to engage the pressure operated input clutch 5. The control unit 101 is further configured to control the engagement of the pressure actuated transmission clutch 15 in a way to control the speed of the output shaft 16 and the speed of a propeller which is connected to the output shaft 16. For these purposes the control unit 101 contains electronic components and hydraulic components like valves for the control of oil flow and oil pressure. The control unit 101 further includes interfaces to exchange data with a control unit of the combustion engine 1, the electric drive motor 2 and/or other control units of the water vessel. The control unit 101 may additionally control oil pressure and oil flow for the lubrication of elements in the transmission 3 and in the hybrid module 20.
Fig. 2 shows schematically the steps of the proposed method to engage the pressure operated input clutch 5. In a first step a) the electric drive motor 2 is started and the combustion engine 1 is started by the electric start motor 8. In the following step b) the rotation speed of the electric drive motor 2 is adjusted to drive the oil pump 6 with a speed which is sufficient to provide the required pressure to engage the input clutch 5. After that, the pressure actuated input clutch 5 can be engaged in step c). The correct pressure and oil flow rate to engage the input clutch 5 can be set and controlled by means of control unit 101. By engaging the input clutch 5 the combustion engine 1 is connected to the transmission input shaft 4. Additionally a preferred method is shown in Fig. 2 which includes a step b1) between steps b) and c). In step b1) the rotation speed of the electric drive motor 2 is adjusted to synchronize the rotation speed of the transmission input shaft 4 with the engine speed, i.e. with the rotation speed of the crank shaft 19.
Such a synchronization of the rotation speeds at the input side and the output side of the input clutch 5 ensures a smooth engagement of the input clutch 5 in the following step c). This is to avoid slipping effects and detrimental torque peaks in the marine hybrid drive unit 100 and to minimize tear of the clutch elements, particularly the friction disks of input clutch 5. The preferred method with the step of synchronizing the rotation speeds allows the use of an input clutch in form of a form fitting clutch, for example a dog clutch, instead of a friction clutch. A form fitting clutch requires less space and transmits higher torque compared to friction clutches.

Referals

1: combustion engine
2: electric drive motor
3: transmission
4: transmission input shaft
5: input clutch
6: oil pump
7: gear step
8: electric start motor
9: crankshaft
10: motor shaft
11: module housing
12: input element
13: output element
14: transmission housing
15: transmission clutch
16: output shaft
17: first spur gear
18: second spur gear
19: toothing
20: hybrid module
21: module input shaft
100: marine hybrid drive unit
101: control unit

Claims

Method to engage a pressure operated input clutch (5) of a marine hybrid drive unit (100) to connect a combustion engine (1) with a transmission input shaft (4) of the hybrid drive unit (100),
wherein the marine hybrid drive unit (100) comprises the combustion engine (1), an electric drive motor (2) and a transmission (3),

wherein the combustion engine (1) comprises an electric start motor (8),

wherein the transmission input shaft (4) can be driven in a combustion engine mode solely by the combustion engine (1), in an electric propulsion mode solely by the electric drive motor (2) and in a combined mode by the combustion engine (1) and the electric drive motor (2),

wherein the electric drive motor (2) is permanently connected to the transmission input shaft (4), and

wherein a pressure for actuating the input clutch (5) is provided by an oil pump (6) which is driven by the transmission input shaft (4),

the method comprising the steps:
a) starting the combustion engine (1) by the electric start motor (8) and starting the electric drive motor (2),

b) adjusting the rotation speed of the electric drive motor (2) to drive the oil pump (6) with a speed which is sufficient to provide enough pressure to engage the input clutch (5),

c) engaging the input clutch (5).
Method according to claim 1, wherein a rotation speed of the electric drive motor (2) is adjusted to synchronize a rotation speed of the transmission input shaft (4) with an engine speed of the combustion engine (1) before engaging the input clutch (5).
Method according to claim 1 or 2, wherein the marine hybrid drive unit (100) is switched in the combustion engine mode and the electric drive motor (2) is switched to a generator mode after the combustion engine (1) has reached a preset engine speed.
Method according to claim 3, wherein the preset engine speed is set to a value in a range between 600 rpm and 800 rpm.
Marine hybrid drive unit (100) comprising a control unit (101), which is configured to execute a method according to one of the preceding claims.
Marine hybrid drive unit (100) according to claim 5, wherein the electric drive motor (2) is part of a hybrid module (20), said hybrid module (20) further comprising a module input shaft (21) being connected to a crank shaft (9) of the combustion engine (1), the pressure actuated input clutch (5) and at least one gear step (7) between the electric drive motor (2) and the transmission input shaft (4),
wherein the pressure actuated input clutch (5) comprises an input element (12) and an output element (13), wherein the input element (12) is connected to the module input shaft (21), and wherein the output element (13) is connected to the transmission input shaft (4).
Marine hybrid drive unit (100) according to claim 6, wherein the electric drive motor (2) is permanently connected to the transmission input shaft (4) via the output element (13) of the input clutch (5).
Marine hybrid drive unit (100) according to one of claims 5 to 7, wherein the control unit is further configured to execute a backup-method to start the combustion engine (1) by the electric drive motor (2) in case of a failure of the electric start motor (8), said backup-method comprising the following steps:
a) starting the electric drive motor (2),

b) adjusting the rotation speed of the electric drive motor (2) to drive the oil pump (6) with a speed which is sufficient to provide enough pressure to engage the input clutch (5),

c) engaging the input clutch (5) and

d) starting the combustion engine (1) by means of the electric drive motor (5).