Improved reliability transmission system for electric outboard motors

Abstract

The present invention relates to a transmission system (1) for an outboard electric motor (21). Said system (1) is configured to be connected to said electric motor (21) at one end and to a boat propeller (3) at the other end, such that the rotation of said motor (21) is transmitted to said propeller (3) by said transmission system (1). Said transmission system (1) is without a gearbox.

Description

Title of the invention: Improved reliability transmission system for electric outboard motors technical field

[0001] The present invention relates to the field of electric motors for boats.

[0002] The present invention relates in particular to the field of outboard motors. Outboard motors are boat propulsion systems comprising, in a single unit, the engine, transmission and propeller propelling the boat, the lower part of the outboard motor being called the base and including the transmission and propeller.

[0003] The present invention relates more specifically to a transmission system for an outboard electric motor whose design allows for simplified use and reduces maintenance needs.

[0004] The present invention also relates to a propulsion system equipped with such a transmission system and an outboard-type vehicle equipped with such a propulsion system.

[0005] The present invention will thus find many advantageous applications in the design of marine vehicles. Technological background

[0006] Electric boat motors, particularly high-power motors, are based on pre-existing thermal bases, originally designed for internal combustion engines. These thermal bases are thus limited by their design, which is adapted to thermal engines.

[0007] It appears, in particular, that standard thermal outdrives are limited in maximum torque. For a 200-horsepower engine, the torque transmission capacity of an associated outdrive is limited to approximately 180 Nm. This transmission capacity stems from the structure of the outdrive and the materials used. However, a 200-horsepower electric motor can generate a torque of 400 Nm, more than double the capacity of the thermal outdrive.

[0008] Furthermore, electric motors generate, on the one hand, high and continuous torque peaks, and on the other hand, significant variations during acceleration and changes of direction, thus placing even greater stress on the lower unit. This excessive stress results in faster wear, increased fragility, and a need for frequent maintenance of the lower unit, particularly if the transmission is subjected to intense load cycles. The most frequent failures occur in the gears.

[0009] Furthermore, the Applicant observes that thermal transmissions consist of a large number of parts, which increase the complexity of the transmission and each of which is susceptible to wear or degradation. Maintenance costs and the risk of breakdowns are thus increased, particularly compared to internal combustion engine propulsion systems due to the higher torque of electric motors. The large number of parts also increases the overall weight of the transmission and reduces its energy efficiency, and therefore its propulsion efficiency.

[0010] Thus, torque, wear and maintenance constraints hinder the efficient deployment of electric motors in the marine sector, limiting their adoption due to high costs, reduced reliability and limited performance.

[0011] The Applicant therefore submits that there is currently no satisfactory alternative transmission system for an electric outboard motor that is capable of withstanding the high torque levels generated by electric motors without suffering premature wear. Summary of the invention

[0012] The present invention aims to improve the current situation described above.

[0013] The present invention is aimed more particularly at overcoming the following drawbacks: above by offering a transmission system optimized specifically for electric motors, capable of handling high torques while minimizing maintenance needs.

[0014] To this end, the object of the present invention relates in a first aspect to a transmission system for an outboard electric motor, the system being configured to be connected to the electric motor at a first end and to a boat propeller at a second end, so that the rotation of the motor is transmitted to the propeller by the transmission system.

[0015] It is understood here that, by its very nature, the transmission system is configured to be associated with an outboard electric motor, that is to say, to be integrated within an electric propulsion system of an outboard-type boat. The transmission system is thus configured to be integrated into a lower unit.

[0016] The rotation of the engine sets the transmission system in motion, or at least the mechanical part of the transmission system, and the motion of the transmission system in turn sets the propeller in rotation. In particular, the rotational speed and torque between the engine and the propeller can be modified via the transmission system by a reduction ratio, as described below. The reduction ratio allows the input rotational speed to be divided to multiply the transmitted torque, or vice versa.

[0017] The transmission system can also be configured to redirect the rotational motion between the engine rotation and the propeller rotation. In particular, it is common to designate an engine that creates a rotational motion about a substantially vertical axis, while the propeller must rotate about a substantially horizontal axis to allow the boat to move. The transmission system thus makes it possible to transform a first vertical rotational motion into a second horizontal rotational motion.

[0018] Advantageously, the transmission system is devoid of a reversing gearbox.

[0019] A person skilled in the art understands that the reversing gearbox is the nautical equivalent of a gearbox in an automobile. The reversing gearbox allows the transmission system to switch between several operating modes, generally forward, reverse, and neutral. Notably, unlike a gearbox, the reversing gearbox offers only one reduction ratio for forward.

[0020] The Applicant submits that these functions are inherited from thermal transmission systems. Neutral is necessary to allow the thermal engine to start without torque transmission and to stop the propeller without shutting off the engine, and the combination of forward and reverse gears allows the propeller's direction of rotation to be reversed from the same engine rotation.

[0021] On the contrary, in the context of an electric motor transmission system, these functions become superfluous. Indeed, an electric motor can start instantly without requiring a neutral position, and torque can be transmitted directly to the propeller without risk, generating maximum torque as soon as the motor starts. The electric motor can also stop freely without needing to remain running to restart. Furthermore, the electric motor can reverse its direction of rotation by electronically reversing its polarity, resulting in a transition between forward and reverse without any change to the transmission system. Thus, it is possible to ensure a smooth transition between the different operating modes based on the advantages of the electric motor, even in the absence of a reversing gearbox.

[0022] The Applicant therefore submits that the mechanical components of the reversing gearbox are superfluous mechanical parts, which unnecessarily increase the complexity of the transmission system and are each susceptible to wear and breakage. Furthermore, the mechanical shifting between neutral, forward, and reverse is less smooth than direct control of the electric motor. Moreover, since the reversing gearbox generally lacks different forward speeds, the reduction ratio remains the same with or without a reversing gearbox. A transmission system dedicated to electric motors and without a gearbox The reversing system thus allows for the same functionalities while offering a simplified mechanism, which reduces wear, the risk of failure and improves the transition between forward, reverse and stopping.

[0023] The Applicant submits, in particular, that eliminating the reversing gearbox means that an oil change is only required after 10,000 hours of use. Maintenance costs are therefore significantly reduced and durability increased, with a maintenance cycle less frequent than conventional systems. Furthermore, such a transmission system is viable in both high-power marine and river applications.

[0024] Removing the reversing gearbox also facilitates sizing adapted to high torques. The transmission system according to the invention thus preferably has a torque transmission capacity of 400 Nm for an 80 to 300 horsepower engine, greatly exceeding the 180 Nm limit of equivalent thermal drives.

[0025] In particular, the removal of the reversing gearbox results in a lighter transmission system for the same torque transmission capacity. Designing transmission systems adapted to higher torques may result in a heavier structure than prior art systems, but one from which unnecessary weight is still removed.

[0026] It is also understood that eliminating superfluous parts results in a system that is easier to install, less expensive to manufacture, and offers better energy efficiency. This invention thus encourages the adoption of electric solutions in boating.

[0027] Thanks to the present invention, the transmission system provides superior robustness, performance, and reliability compared to prior art solutions, while offering a simpler and less expensive design. The transmission system thus enables efficient and energy-saving navigation.

[0028] In an advantageous embodiment of the present invention, the system comprises: - a first shaft configured to be connected to the electric motor and featuring a first pinion; - a second shaft configured to be connected to the propeller and featuring a second pinion, the first pinion being engaged with the second pinion; and - a housing forming an external envelope of the transmission system, the housing containing the first shaft and the second shaft.

[0029] In other words, the two pinions are fixed together and mesh with each other to form a gear. The two pinions allow, in particular to define the reduction ratio of the transmission system, based on their respective number of teeth. It is understood here that the meshing of two gears corresponds to the simplest solution for defining the reduction ratio of the transmission system and for properly orienting the rotation of the propeller relative to that of the engine. The transmission system according to the invention therefore comprises a single pair of gears.

[0030] Preferably, the gears are made of high-strength steel to withstand mechanical wear and are designed to minimize energy losses in the transmission. As stated above, a simple design minimizing the number of parts also helps to minimize losses and wear. In this way, a simple and highly robust transmission system is obtained, capable of transmitting high torques.

[0031] In parallel, the housing encloses the internal components of the transmission system and is designed to ensure their sealing and protection. For example, the housing is equipped with double sealing rings at the connection between the transmission system and the motor, as well as at the connection between the transmission system and the propeller.

[0032] Preferably, the first pinion and the second pinion are configured so that the first shaft extends along a first axis and the second shaft extends along a second axis separated at an angle with respect to the first axis.

[0033] As stated above, in an outboard propulsion system, the motor generally has a substantially vertical axis of rotation, while the propeller has a substantially horizontal axis of rotation. The two pinions must therefore be configured to allow reorientation between the first and second axes. The angle is preferably approximately 90°. Thus, the first shaft is configured to extend vertically under the electric motor so as to pass, at least partially, below the waterline, and the second shaft is configured to define a horizontal axis of rotation for the propeller to propel the boat. Obviously, depending on the intended design of the motor and / or propeller to which the transmission system is configured to be connected, it is possible to adjust the arrangement and design of the shafts and pinions.

[0034] The gears correspond in particular, for example, to conical gears, helical gears, or any other means allowing the shafts to be arranged respectively according to the desired angle.

[0035] Preferably, the housing is made of a corrosion-resistant material.

[0036] It is understood here that the corrosion resistance of the casing ensures its durability in the seabed.

[0037] More generally, the components of the transmission system are made of corrosion-resistant materials and / or treated to withstand marine conditions, i.e. in particular salt water and humidity, in order to ensure a long service life without frequent maintenance.

[0038] Preferably, the transmission system is configured to have IP 6K9K grade sealing, so as to ensure long-term sealing for a system intended to operate continuously underwater.

[0039] It is also understood that the sealing of the transmission system also relies on the system's attachment to the other components, in particular the attachment between the transmission system and the propeller, which is intended to be submerged. As stated above, sealing can be achieved at the transmission system attachment point using double sealing rings.

[0040] In one embodiment, the system has a reduction ratio between 1:1 and 3:1, preferably between 1.5:1 and 2:1, preferably substantially equal to 1.8:1.

[0041] As stated previously, the reduction ratio is defined by the gears.

[0042] The reduction ratio corresponds to the ratio between the input speed of the transmission system, i.e., at the engine, and the output speed of the transmission system, i.e., at the propeller. In other words, for a reduction ratio of 1.8:1, 1.8 input revolutions are converted into 1 output revolution.

[0043] A person skilled in the art also understands that reducing the rotational speed also corresponds to a multiplication of the torque.

[0044] The Applicant submits that a ratio of approximately 1.8:1 makes it possible to achieve a wide range of propeller speeds, suitable for various navigation needs, while maximizing fuel efficiency and providing enhanced torque for high-performance, fuel-efficient navigation. An engine speed of 0 to 5000 rpm is converted into a propeller speed of 0 to 2778 rpm, and a maximum torque of 400 Nm at the engine is converted into 700 Nm at the propeller, thus providing high thrust without requiring a larger engine.

[0045] In one embodiment, the system is adapted for an electric motor with a power output of at least 80 horsepower.

[0046] In other words, the system is suitable for a high-power electric motor. As stated previously, previous transmission systems for high-power motors are based on thermal bases and are not suitable for transmitting the high torques associated with high-power electric motors. Furthermore, simplifying the transmission system facilitates sizing the transmission system for high torques. It is anticipated preferably a transmission system sized to support a torque of 400Nm at the engine and a torque of 700Nm at the propeller.

[0047] Preferably, the system is adapted for an electric motor with a power output between 80 and 300 horsepower.

[0048] In one embodiment, the system includes means for fixing to an engine block comprising the engine.

[0049] In a conventional design, the transmission system is attached to a motor unit, which is itself assembled to the boat. The motor unit includes the electric motor, as well as other components necessary for its operation, for example, motor control means and a human-machine interface associated with these control means.

[0050] The fixing means advantageously include stainless steel supports and mounts, ensuring stable positioning of the transmission components and resistance to shocks and vibrations from navigation at sea.

[0051] In particular, the transmission system has a simple structure that is easily adaptable to a wide range of engine and propeller models. Such adaptation corresponds, for example, to the provision of dedicated mounting means, such as a specific propeller bracket. This adaptation may also correspond to appropriately sizing the transmission system, or more generally the lower unit, particularly according to the engine. For example, the size of the first shaft, as described above, is adapted according to the engine and / or the boat in question.

[0052] In one embodiment, the transmission system includes closed-circuit lubrication means.

[0053] In other words, the transmission system includes an internal lubrication system to reduce wear and ensure the longevity of the transmission system. In particular, the lubrication means include a high-viscosity oil suitable for the marine environment.

[0054] According to a second aspect, the present invention relates to a propulsion system for an outboard-type vehicle comprising: - an engine block containing an electric motor; - a transmission system according to the first aspect of the present invention; and - a propeller, the transmission system being connected to the electric motor at the first end and to the propeller at the second end.

[0055] The propulsion system thus corresponds to an outboard motor. It is understood here that the propulsion system is characterized in particular by the absence of a gearbox in the transmission system.

[0056] As stated previously, since the motor unit is based on an electric motor, it does not require a neutral position for starting or stopping and can reverse its rotation to alternate between forward and reverse, without requiring any associated mechanical device. This propulsion system is therefore simpler and more efficient compared to the prior art. The transition between forward, reverse, and stopping is also smoother, with instantaneous transmission of the torque generated by the motor to the propeller for rapid and responsive propulsion.

[0057] In particular, the motor unit includes an electronic board, which is configured to reverse the polarity of the current flowing through the motor. The polarity reversal thus results in a reversal of the motor's direction of rotation and a transition between forward and reverse, which is controlled entirely electronically without any mechanical components being required.

[0058] Furthermore, the propulsion system, like the transmission system, is configured to operate in a marine or riverine environment. Advantageously, IP 67-rated sealing is provided for the entire propulsion system, particularly in combination with superior sealing for the submerged parts of the system as described above.

[0059] According to a third aspect, the present invention relates to an outboard-type vehicle equipped with a propulsion system according to the second aspect of the present invention.

[0060] The outboard type vehicle thus corresponds to a nautical vehicle, adapted for river and / or maritime navigation.

[0061] Thus, by the various functional and structural technical characteristics above, the Applicant proposes a transmission system for an outboard electric motor, as well as a propulsion system and a vehicle integrating such a transmission system, which eliminates superfluous elements inherited from internal combustion engines, in particular for greater power, reliability, ease of use, and better energy efficiency. Description of the figures

[0062] Other features and advantages of the present invention will become apparent from the description of the particular and non-limiting embodiment of the present invention below, with reference to the attached [Fig. 1], in which:

[0063] Fig. 1 illustrates a schematic view of an outboard-type vehicle, in which a transmission system according to an embodiment of the present invention connects the electric motor and the propeller of the vehicle. Detailed description

[0064] A transmission system and an outboard motor equipped with this system will now be described in what follows with reference to [Fig. 1]. The same elements are identified with the same reference symbols throughout the following description.

[0065] As indicated in the preamble to the description, electric boat motors largely adopt the structure and logic of pre-existing thermal solutions. However, electric motors have their own operating constraints, which negatively impact the efficiency and lifespan of the associated transmission system when it is based on a transmission for a thermal engine.

[0066] One of the objectives of the present invention is to propose a dedicated transmission system for an electric motor, which has better wear resistance and exploits the performance of electric motors.

[0067] Following the example in [Fig. 1], a nautical vehicle 4 is envisaged here, in particular an outboard-type vehicle. By definition, the vehicle 4 is equipped with an outboard propulsion system, or outboard motor.

[0068] The propulsion system includes a motor block 2 equipped with an electric motor 21 and other components necessary for the control or fixing of the electric motor 21. The electric motor 21 preferably corresponds to a high power motor, and most preferably has a power output between 80 and 300 horsepower.

[0069] The propulsion system also includes a propeller 3, corresponding to a boat propeller. The rotation of the propeller 3 thus enables the movement of the vehicle 4.

[0070] Between the motor 21 and the propeller 3, the propulsion system includes a transmission system 1. The transmission system 1 is attached to the motor block 2, and by extension to the vehicle 4, by means of attachment (not shown), for example by a set of stainless steel supports and mounts. The transmission system 1 is thus connected on one side to the electric motor 21, and on the other side to the propeller 3. The transmission system 1 is configured to transmit the rotation and torque generated by the motor 21 to the propeller 3. The transmission of the motion of the motor 21 may also be accompanied by a conversion of this motion, in particular a modification of the rotational speed and torque, as well as a conversion of the rotational motion of the motor 21 into a rotational motion of the propeller 3, without these two motions necessarily being coaxial.

[0071] A traditional transmission system, based on the structure of internal combustion engines, is equipped with a reversing gearbox, itself derived from the gearboxes used in automobiles. The reversing gearbox has a first gear that converts the movement of the engine 21 into a first rotation of the propeller 3, corresponding to a forward movement of the vehicle 4, a second gear allowing the movement of the engine 21 to be converted into a second rotation of the propeller 3, corresponding to a reverse movement of the vehicle 4, and a mechanism allowing alternating between forward, reverse and neutral, in which the movement of the engine 21 is not transmitted to the propeller 3.

[0072] In accordance with the underlying concept of the invention, the transmission system 1 according to the invention is here without a reversing gearbox. On the contrary, the transition between forward and reverse is managed at the electric motor 21, which can reverse its direction of rotation by reversing the polarity of the current flowing through it. Furthermore, the electric motor 21 does not require a neutral position and can freely stop or start with direct torque transmission to the propeller 3.

[0073] Thus, in the example of [Fig. 1], the transmission system 1 comprises a first shaft 11 connected to the electric motor 21, a second shaft 13 connected to the propeller 3, and a gear 12 between the first shaft 11 and the second shaft 13. The gear 12 is simply composed of a first pinion 12a associated with the first shaft 11 and a second pinion 12b associated with the second shaft 13, the two pinions 12a and 12b meshing with each other. Such a design allows for simple transmission of rotational motion with a minimum number of parts, thereby minimizing energy losses, weight, cost, and wear of the transmission system 1. To ensure smooth operation, the transmission system 1 preferably includes closed-circuit lubrication means, particularly at the pinions 12a and 12b.

[0074] As stated previously, the transmission system 1 can convert the rotational motion of the motor 21 to adapt it to the desired rotation of the propeller 3. Here, the motor 21 rotates about a first axis X and the propeller 3 rotates about a second axis Y, which are substantially orthogonal. The first shaft 11 thus extends along the first axis X, the second shaft 13 extends along the second axis Y, and the gears 12a, 12b are configured to convert the rotation about the first axis X into a rotation about the second axis Y. The gears 12a, 12b correspond, for example, to bevel or helical gears.

[0075] Furthermore, the rotational speed and torque of the motor 21 are also converted according to the gears 12a, 12b. The gears 12a, 12b thus define a reduction ratio of between 1:1 and 3:1, preferably between 1.5:1 and 2:1. Most preferably, the reduction ratio is substantially equal to 1.8:1. For example, a motor 21 is configured to rotate up to 5000 rpm, such a rotation being converted into a propeller rotation of 2778 rpm. The transmitted torque is multiplied in parallel. In particular, the transmission system 1 is configured to transmit a torque of up to 400 Nm at the motor 21 and the first shaft 11, converted into 700 Nm at the propeller 3 and the second shaft 13.

[0076] The transmission system 1 also includes a housing 14, which encloses the first shaft 11, the second shaft 13, and, by extension, the gear 12. The housing 14 forms an external enclosure for the transmission system 1 to protect its components. The housing 14 is particularly corrosion-resistant and designed to ensure the transmission system 1 is watertight. The housing 14 is, for example, coupled with watertight fastening means for the transmission system 1 on the motor 21 and the propeller 3, for example, double sealing rings. The first shaft 11, the second shaft 13, and the gears 12a, 12b are preferably also designed to withstand an aqueous environment, particularly a marine environment, and are configured to resist corrosion, marine conditions, humidity, etc. The transmission system 1 is thus designed to be watertight, for example, to IP6K9K rating.Similarly, lubrication methods can be based on a high-viscosity oil suitable for the marine environment. The propulsion system in general can have an IP67 rating for watertightness.

[0077] Thus, it will be understood that the present invention provides a transmission system adapted for an outboard electric motor, which greatly simplifies the initial structure derived from internal combustion engine lower units. Such a transmission system makes it possible to take advantage of the operation of electric motors by enabling rapid starting and quick, smooth shifting between forward and reverse. A simple design adapted to the transmitted forces also ensures minimal wear, easy and infrequent maintenance, limited weight, and improved energy efficiency.

[0078] The present invention also provides for a propulsion system equipped with this transmission system, as well as a vehicle equipped with such a propulsion system.

[0079] It should be noted that this detailed description relates to a particular embodiment of the present invention, but in no way does this description limit the scope of the invention; on the contrary, its purpose is to remove any possible inaccuracy or misinterpretation of the following claims.

[0080] It should also be noted that the reference signs in parentheses in the following claims are in no way intended to be limiting; these signs are solely intended to improve the intelligibility and understanding of the following claims and the scope of the protection sought.

Claims

Demands

1. Transmission system (1) for an electric outboard motor (21), said system (1) being configured to be connected to said electric motor (21) at a first end and to a boat propeller (3) at a second end, so that the rotation of said motor (21) is transmitted to said propeller (3) by said transmission system (1), characterized in that said transmission system (1) is devoid of a reversing gearbox.

2. Transmission system (1) according to claim 1, which comprises: - a first shaft (11) configured to be connected to said electric motor (21) and having a first pinion (12a); - a second shaft (13) configured to be connected to said propeller (3) and having a second pinion (12b), said first pinion (12a) being engaged with said second pinion (12b); and - a housing (14) forming an external enclosure of said transmission system (1), said housing (14) containing said first shaft (11) and said second shaft (13).

3. Transmission system (1) according to claim 2, wherein said first pinion (12a) and said second pinion (12b) are configured such that said first shaft (11) extends along a first axis (X) and said second shaft (13) extends along a second axis (Y) separated at an angle with respect to said first axis (X).

4. Transmission system (1) according to claim 2 or 3, wherein said housing (14) is made of a corrosion-resistant material.

5. Transmission system (1) according to any one of claims 1 to 4, which has a reduction ratio of between 1:1 and 3:1, preferably between 1.5:1 and 2:1, preferably substantially equal to 1.8:

1.

6. Transmission system (1) according to any one of claims 1 to 5, which is adapted for an electric motor (21) having a power of at least 80 horsepower.

7. Transmission system (1) according to any one of claims 1 to 6, which includes means for fixing to an engine block (2) comprising said engine (21).

8. Transmission system (1) according to any one of claims 1 to 7, which includes closed-circuit lubrication means.

9. Propulsion system for outboard-type vehicle (4) comprising: - a motor block (2) having an electric motor (21); - a transmission system (1) according to any one of claims 1 to 8; and - a propeller (3), said transmission system (1) being connected to said electric motor (21) according to said first end and to said propeller (3) according to said second end.

10. Outboard-type vehicle (4) equipped with a propulsion system according to claim 9.

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