EP4671508A1

EP4671508A1 - NOISE REDUCTION HOUSING

Info

Publication number: EP4671508A1
Application number: EP24184344.0A
Authority: EP
Inventors: Mattia Caracristi; Michele Zottele
Original assignee: ZF Friedrichshafen AG; ZF Padova SRL
Current assignee: ZF Friedrichshafen AG; ZF Padova SRL
Priority date: 2024-06-25
Filing date: 2024-06-25
Publication date: 2025-12-31

Abstract

The present disclosure relates to a noise reduction case (10) for a transmission (102) of a propulsion unit (100) of a watercraft (200), the propulsion unit (100) comprising a motor (112) for driving a propeller (106) via the transmission (102). The propulsion unit further comprises an engine bed (104) for supporting the motor (112). The noise reduction case comprises a structural frame (12) mechanically couplable to the propulsion unit (100). The noise reduction case (10) further comprises a noise reduction cladding (20) arranged on the structural frame (12) for reducing a noise of the transmission (102). The noise reduction cladding (20) comprises a displacement section (30; 34) configured to deform in response to a relative movement between the transmission (102) and the engine bed (104) of the propulsion unit (100). The invention further relates to a method for mounting such a noise reduction case (10), a propulsion unit (100) with such a noise reduction case (10), and a watercraft (200) with such a propulsion unit (100).

Description

Technical field

The present disclosure relates to a noise reduction case for a transmission of a propulsion unit of a watercraft, to a method for mounting such a noise reduction case to a propulsion unit, to a propulsion unit with such a noise reduction case, and to a watercraft with such a propulsion unit.

Prior art

Most of an electric or hybrid boat's life is spent operating under 10 knots. At this speed, wind and water flow noise is still minimal and the most dominant noise experienced by boat drivers and passengers of electric and hybrid boats is the marine transmission. EP 2 664 536 B1 relates to a system with a propeller shaft for supplying a rotary drive power to a propulsion element.

Description of the invention

The present disclosure relates to a noise reduction case for a transmission of a propulsion unit of a watercraft, the propulsion unit comprising a motor for driving a propeller via the transmission and an engine bed for supporting the motor. The noise reduction case may comprise a case, a box or a covering. Reducing a noise may comprise reducing a noise perceived outside of the noise reduction case. A watercraft may be any vehicle for moving in or on water, for example a boat, which may be a recreational boat, a ship, or a submarine. The propulsion unit may be a device or assembly configured to propel the watercraft. The transmission may be a mechanical device or assembly configured to transmit a mechanical power to the propeller and additionally or alternatively for changing a speed or a direction of a mechanical rotation. The motor may be an electric motor, a hybrid motor, a combustion engine, and/or another device able to provide mechanical power to the propeller. The propeller may be a propeller or screw adapted for use in water. The engine bed is a structure for supporting the motor and may be an integral part of the structure of the watercraft, be arranged within it or be attached to it. The engine bed may provide an opening or a passage for a shaft of the propulsion unit to transmit a mechanical power to the propeller. The engine bed may also support the transmission.
The propulsion unit may experience significant movement during operation, in particular, it may experience significant relative movements. For example, the transmission may experience a displacement of up to 10 mm relative to the engine bed during operation of the propulsion unit. This may comprise a movement along a vertical direction with a displacement of up to 10 mm in both directions from a resting position, resulting in a total range of movement of up to 20 mm. The displacement or the movement may comprise a vibration or a shaking. The transmission may be coupled to the propeller and move with it during operation of the propulsion unit. The displacement may be due to a power provided by the motor. The motor may experience a displacement relative to the engine bed, be fixed to the engine bed, move with the transmission, or move with the engine bed. The displacement may vary depending on the power, speed, and additionally or alternatively further settings of the motor. The motor and additionally or alternatively the transmission may be perceived as very loud during operation. The transmission may comprise gear teeth that are between 20% to 30% wider than is common for reducing an operating noise. The surfaces of the gear teeth may be grinded in a post-processing step to further reduce an operating noise. The thickness of a housing of the transmission may also be increased and ribs of the housing may be distributed so as to reduce a noise of the transmission. A damping system of the propulsion unit may also be optimized to reduce the amplitude and/or frequency of vibrations of the propulsion unit.
The noise reduction case comprises a structural frame mechanically couplable to the propulsion unit, and a noise reduction cladding arranged on the structural frame for reducing a noise of the transmission. The structural frame may comprise flat sheets of material, which may be arranged to form the walls of a box, a case, a covering or a comparable structure. Alternatively, the structural frame may comprise different geometries, for example struts or beams. The structural frame may structurally support the noise reduction case. It may comprise a thickness from 5 mm to 40 mm, for example from 10 mm to 20 mm. A thickness may correspond to a thickness of a material sheet comprising the structural frame. The structural frame may comprise a polymer, for example a thermoplastic material, for example PEEK, ABS or PC. The structural frame may comprise other polymers characterized by chemical resistance, thermal stability, and mechanical strength. The structural frame may be assembled using an epoxy adhesive.
The noise reduction cladding may be arranged on the structural frame through the use of adhesives. For example, it may be glued to the structural frame using acrylic adhesive. Additionally or alternatively, it may be arranged on the structural frame through other means, for example through screws, bolts, nails or other means. The noise reduction cladding comprises a displacement section configured to deform in response to a relative movement between the transmission and the engine bed of the propulsion unit. The displacement section may deform by being compressed between the structural frame and a further part of the propulsion unit, for example the engine bed or the transmission. The displacement section may prevent a collision of the structural frame and a further part of the propulsion unit. It may also deform to improve a noise reduction of the noise of the transmission. It may deform so as to maintain a closed covering of the transmission during operation. A closed covering may mean that the noise reduction case is substantially covering most of the area around the transmission.
The displacement section may absorb a vibration or a displacement of the propulsion unit. The displacement section may provide a degree of mechanical and additionally or alternatively acoustic isolation between the transmission and the engine bed. The displacement section may comprise the same materials as the rest of the noise reduction cladding. Alternatively, it may comprise only some of the materials as the rest of the noise reduction cladding. The displacement section may form an extension of the rest of the noise reduction cladding and be flush against it. It may comprise the same structure and have a comparable cross section. The displacement section may not be directly attached to the structural frame, and may extend beyond it. For example, it may extend beyond a lower limit of the structural frame. It may extend along a space between the structural frame and the engine bed formed around the transmission.
The noise reduction case may comprise substantially one part, or it may comprise multiple parts, for example be composed of two sections. It may for example comprise an upper and a lower section, which may be assembled together to form the noise reduction case. The lower section may comprise the displacement section. Through the features and the structure of the noise reduction case described above, a noise of a transmission may be effectively and cheaply reduced. This may enable a more comfortable and enjoyable experience of passengers or personnel on a watercraft equipped with the described noise reduction case. It may also enable a reduction of vibrations, further improving comfort. The noise reduction case may further reduce or eliminate the need for hearing protection, as a noise level may be reduced to safe or safer levels. This is particularly advantageous if the watercraft is operated at low speeds, e.g. under 10 knots, via an electric or hybrid motor. The noise reduction case may be easily removable, for example to perform an inspection of the transmission, an oil check or an oil refill.
In an embodiment, the noise reduction case comprises a transmission coupling device configured to enable a coupling of the noise reduction case to the transmission. Additionally, the displacement section is configured to maintain a contact between the noise reduction case and the engine bed. The coupling may comprise a mechanical coupling, for example fixedly attaching the noise reduction case to the transmission. It may comprise coupling the structural frame to the transmission. The transmission may comprise a housing, which may be a bell housing. The housing of the transmission may move with the transmission and experience a displacement during operation. The coupling device may comprise one or multiple brackets, plates, screws, latches and additionally or alternatively other implements. It may comprise a metal plate configured to create a fixed connection between the housing of the transmission and the structural frame with screws. For example, four screws may be used.
The displacement section may be configured to be in contact with the engine bed. The displacement section may be configured to be in a compressed state when the propulsion unit is at rest. It may be configured to maintain a closed covering of the transmission while the noise reduction case is moving with the transmission relative to the engine bed. The displacement section may be arranged at the bottom of the noise reduction case, that is, the side towards the engine bed. The displacement section may comprise a substantially rectangular footprint and may form a skirt-like shape around the bottom of the noise reduction case. It may also dampen a movement of the transmission and additionally or alternatively of the structural frame during operation. By providing a noise reduction case as described, a particularly effective and efficient noise reduction may be provided. As the relative movement between the transmission and the engine bed may cause or be related to a significant amount of noise, an insulation of this source may be particularly effective in reducing noise. This may lead to a more comfortable and quieter experience for passengers and personnel on board of the watercraft.
In an embodiment, the noise reduction case comprises a bed coupling device configured to enable a coupling of the noise reduction case to the engine bed. Additionally, the displacement section is configured to maintain a contact between the noise reduction case and the transmission during the movement of the transmission relative to the engine bed. The bed coupling device may be an analogous device to the transmission coupling device described previously. It may comprise one or multiple brackets configured to fixedly attach the noise reduction case to the engine bed, for example through screws, for example four screws. It may be configured to hold the noise reduction case in a predetermined position relative to the engine bed.
The displacement section may be configured to maintain a contact with a housing of the transmission, such as a bell housing. It may be configured analogously to the previously described embodiment. It may be arranged inside the noise reduction case, for example on a side through which a shaft of the transmission enters the noise reduction case. It may dampen a movement of the transmission and additionally or alternatively of the structural frame. By providing a noise reduction case as described, a particularly effective and efficient noise reduction may be provided. As the movement of the transmission may cause or be related to a significant amount of noise, an insulation of this source may be particularly effective in reducing noise. This may lead to a more comfortable and quieter experience for passengers and personnel on board of the watercraft.
In an embodiment, the noise reduction cladding comprises a sound reflecting layer. The sound reflecting layer may be configured to reflect soundwaves, thereby providing a noise reduction. The sound reflecting layer may be arranged such that it fully or mostly covers a transmission, such that sound coming from it gets reflected back to the transmission, reducing a noise outside of the noise reduction case. The sound reflecting layer may be arranged parallel to the structural frame and additionally or alternatively may be arranged directly next to or on it. It may be arranged on the outside and additionally or alternatively on the inside of the noise reduction case. The sound reflecting layer may be glued to the structural frame, for example with acrylic adhesive. The sound reflecting layer may constitute the only layer of the noise reduction cladding or may be one of multiple layers of the noise reduction cladding.
In an embodiment, the sound reflecting layer comprises a closed cell material. The closed cell material may be a rubber material, for example Mousse rubber, EPDM or other rubbers. The closed cell structure of the sound reflecting layer may enable a particularly effective reflection of sound waves. The material may be particularly well suited for use in the displacement section and may be particularly well adapted to absorb or dampen vibrations. It may be adapted to mechanically and acoustically isolate the noise reduction case and additionally or alternatively the transmission from the rest of the watercraft.
In an embodiment, the sound reflecting layer comprises a thickness between 30 mm and 60 mm, for example between 40 mm and 50 mm, such as 45 mm. The thickness may be a thickness as measured perpendicular to a contact surface with the structural frame. The thickness may be substantially uniform along the entire noise reduction case. The thickness may vary, for example be larger, in the displacement section. The thickness may be configured to reflect a specific frequency or range of frequencies particularly well, for example frequencies emitted by the transmission.
By providing a sound reflecting layer as described above, the noise reduction properties of the noise reduction case may be further improved. Soundwaves that are reflected back may not be heard or be heard less by passengers and personnel, thereby providing a more comfortable and enjoyable experience. By using the same layer in the displacement section, the noise reduction case may further be particularly simple, cheap, and effective.
In an embodiment, the noise reduction cladding comprises a sound absorbing layer. The sound absorbing layer may be configured to absorb soundwaves, thereby providing a noise reduction. The sound absorbing layer may be arranged such that it fully or mostly covers a transmission, such that sound coming from it gets absorbed, reducing a noise outside of the noise reduction case. The sound absorbing layer may be arranged parallel to the structural frame and additionally or alternatively to the sound reflecting layer. It may be arranged directly next to or on to the sound reflecting layer. The order of the layers of the noise reduction cladding may also be reversed or different. The sound absorbing layer may be glued to the sound reflecting layer, for example with acrylic adhesive. The sound absorbing layer may comprise the only layer of the noise reduction cladding or may be one of multiple layers of the noise reduction cladding.
In an embodiment, the sound absorbing layer comprises an open cell material. The open cell material may be a rubber material or a resin, for example an expanded melamine resin. The open cell structure of the sound absorbing layer may enable a particularly effective absorption of sound waves. The material may be particularly well suited for use in the displacement section and may be particularly well adapted to absorb or dampen vibrations. It may be adapted to mechanically and acoustically isolate the noise reduction case and additionally or alternatively the transmission from the rest of the watercraft.
In an embodiment, the sound absorbing layer comprises a thickness between 20 mm and 50 mm, for example between 30 mm and 40 mm, such as 35 mm. The thickness may be a thickness as measured perpendicular to a contact surface with the sound reflecting layer or the structural frame. The thickness may be substantially uniform along the entire noise reduction case. The thickness may vary, for example be larger, in the displacement section. The thickness may be configured to absorb a specific frequency or range of frequencies particularly well, for example frequencies emitted by the transmission.
By providing a sound absorbing layer as described above, the noise reduction properties of the noise reduction case may be further improved. Soundwaves that are absorbed may not be heard or be heard less by passengers and personnel, thereby providing a more comfortable and enjoyable experience.
In an embodiment, the noise reduction cladding comprises a pyramidal surface pattern. The pyramidal surface pattern may comprise multiple pyramid shapes arranged on the surface, for example in a grid pattern abutting one another. The pyramidal surface pattern may comprise other shapes, such as cones, tetrahedrons, cubes or ramps. The pyramidal surface pattern may be arranged on an outside surface of the noise reduction case, or additionally or alternatively on an inside surface of the noise reduction case. The pyramidal surface pattern may be configured to reflect, absorb, and additionally or alternatively break up soundwaves to improve a noise reduction. The pyramidal surface pattern may comprise the same material as the sound absorbing layer and additionally or alternatively may be part of it. It may comprise the same material as the sound reflecting layer, and additionally or alternatively further materials. The shape and size of the pyramidal surface pattern may be configured to reduce the noise of a particular frequency or range of frequencies particularly well, for example frequencies emitted by the transmission. The displacement section may comprise a pyramidal surface pattern. By providing the described pyramidal surface pattern, a noise reduction may be improved further. It may provide a particularly strong noise reduction.
In an embodiment, the displacement section comprises a thickness between 40 mm and 60 mm, for example a thickness of 50 mm. The thickness of the displacement section may be related to a displacement of the propulsion unit. For example, it may be configured to provide a remaining thickness of at least 40 mm during the largest displacement. The thickness may be a height, for example as measured from the engine bed to the start of the structural frame. The displacement section may be configured to suspend the structural frame above the engine bed. The thickness may also be a thickness between the housing of the transmission and the structural frame. The thickness may be configured to maintain a minimum distance between the structural frame and the housing of the transmission. The thickness may be a thickness of the displacement section when the propulsion unit is at rest.
The present disclosure relates to a method for mounting a noise reduction case according to one of the previously described embodiments to a propulsion unit of a watercraft. The propulsion unit comprises a motor for driving a propeller via a transmission, and an engine bed for supporting the motor. The method comprises a step of positioning the noise reduction case over the transmission. The positioning may comprise a placing of the noise reduction case on the engine bed. The positioning may be performed before, after, or during an installation of the transmission. If the noise reduction case comprises multiple parts, the positioning may comprise positioning only one of the parts, for example a lower part. The positioning may be performed by hand or by a machine. A guide device, such as a frame, may be used to accurately position the noise reduction case.
The method comprises a step of compressing the displacement section against the propulsion unit by applying a force to the noise reduction case. This may comprise a step of compressing against the engine bed. Additionally or alternatively, this may comprise a step of compressing against the transmission, for example a housing of the transmission. The force may be applied from a top of the noise reduction case or from a side, for example through appropriate holes or ledges in the noise reduction case. The force may be applied through a machine, through a tool or by hand. Compressing the displacement section may comprise using a precompression template. The precompression template may be a device configured to fix or align the noise reduction case to a predetermined position to allow a precise compression. The displacement section may be pre-compressed so that it may be in a compressed state when the propulsion unit is at rest. It may be compressed so that the displacement section may comprise a predetermined thickness when the load is removed. This may enable the displacement section to be particularly springy and to stay in contact with the propulsion unit in all displacement positions and during all operational conditions.
The method comprises a step of mechanically coupling the structural frame to the propulsion unit with the displacement section being in a compressed state. Mechanically coupling may comprise fixing the structural frame to the propulsion unit, for example to a housing of the transmission or to the engine bed. The coupling may comprise the use of a coupling device, which may be configured to fix the structural frame through the use of screws. Mechanically coupling may comprise fixing the noise reduction case to the propulsion unit through the use of brackets. The brackets may be L-shaped, for example having one side configured for attachment to the engine bed and one side for attachment to a side wall of the noise reduction case. The coupling may also be performed using adhesives, straps, and additionally or alternatively other attachment methods.
The method may further comprise a step of removing the load from the noise reduction case, for example by removing a weight from the noise reduction case. The displacement section may then remain in a compressed state. The method may further comprise a step of attaching the upper part of the noise reduction case, for example to the lower part.
By providing a method for mounting the noise reduction case as described, a particularly simple, quick, and effective method of reducing a noise of the propulsion unit is provided. This may provide some or all of the previously described advantages.
The present disclosure relates to a propulsion unit for a watercraft, the propulsion unit comprising a motor for driving a propeller via a transmission and an engine bed for supporting the motor. The propulsion unit comprises a noise reduction case according to a previously described embodiment, wherein the structural frame of the noise reduction case is mechanically coupled to the transmission. The structural frame may be coupled to the transmission according to a previously described embodiment, for example through the use of a transmission coupling device. The structural frame may be fixed to the transmission, for example to a housing of the transmission. The displacement section is in contact with the engine bed of the propulsion unit. It may be compressedly in contact with the engine bed. To be compressedly in contact may comprise to have at least a part of the displacement section in contact, for example direct contact, with the engine bed. It may comprise the displacement section being compressed relative to an unloaded state. The compression may have been applied according to a previously described step of compressing the displacement section.
The present disclosure also relates to a propulsion unit for a watercraft, the propulsion unit comprising a motor for driving a propeller via a transmission and an engine bed for supporting the motor. The propulsion unit comprises a noise reduction case according to a previously described embodiment, wherein the structural frame of the noise reduction case is mechanically coupled to the engine bed. The structural frame may be coupled to the engine bed according to a previously described embodiment, for example through the use of a bed coupling device. The structural frame may be fixed to the engine bed, for example through brackets. The displacement section is in contact with the transmission of the propulsion unit. It may be compressedly in contact with the transmission. The displacement section may be compressed between a side wall of the noise reduction case and a side wall of the housing of the transmission. The noise reduction case may additionally comprise a displacement section which is also in contact, for example compressedly in contact, with the engine bed.
By providing a propulsion unit as described, a particularly quiet propulsion unit may be provided. This may provide some or all of the previously described advantages. It may reduce the intensity of the vibrations and mechanical stress experienced by a watercraft the propulsion unit is mounted to.
The present disclosure further relates to a watercraft with a propulsion unit as previously described. Such a watercraft may be particularly quiet.

Brief description of the figures

Fig. 1 schematically shows a watercraft with a propulsion unit having a transmission and a noise reduction case.
Fig. 2 schematically shows a cross section of a wall of the noise reduction case of fig. 1.
Fig. 3 schematically shows the noise reduction case mounted on the propulsion unit of fig. 1.
Fig. 4 schematically shows an alternative mounting of the noise reduction case on the propulsion unit of fig. 1.
Fig. 5 schematically shows a method for mounting the noise reduction case on the propulsion unit as shown in fig. 3.

Detailed description of the figures

Fig. 1 schematically shows a watercraft 200 with a propulsion unit 100. The propulsion unit 100 comprises a transmission 102, which is surrounded by a noise reduction case 10. The noise reduction case 10 will be described in more detail in relation to the subsequent figures.
Fig. 2 schematically shows a cross-section of a wall of the noise reduction case 10 shown in Fig. 1. It comprises a structural frame 12 and a noise reduction cladding 20. The noise reduction cladding 20 extends parallel to and is glued on to the structural frame 12 with an acrylic adhesive 28. The structural frame 12 and the noise reduction cladding 20 are shown here as extending upwards up to a wavy line, indicating that the upper section of the structure is not shown. The noise reduction cladding 20 further comprises a displacement section 30, which extends downwards beyond the structural frame 12 such that it is not directly attached to the structural frame 12. The layers shown in Fig. 2 are configured to form a case around the transmission 102 to reduce a noise coming from the transmission 102.
The structural frame 12 forms a case structure of the noise reduction case 10, and comprises sheets with a thickness of approximately 15 mm. The sheets are composed of a thermoplastic material, such as PEEK, ABS or PC.
The noise reduction cladding 20 comprises a sound reflecting layer 22, which is directly attached to the structural frame 12 with the acrylic adhesive 28. The sound reflecting layer 22 has a thickness of approximately 45 mm. It comprises mousse rubber EPDM, which is a closed cell expanded rubber material. The sound reflecting layer 22 is arranged to reduce a sound coming from inside the noise reduction case 10 and provide soundproofing for the transmission 102. In particular, the sound reflecting layer 22 is configured to reflect the sound back into the noise reduction case 10.
The noise reduction cladding 20 further comprises a sound absorbing layer 24, which is directly attached to the sound reflecting layer 22 with an acrylic adhesive 28 on a side opposite to the structural frame 12. The sound absorbing layer 24 has a thickness of approximately 35 mm. It comprises expanded melamine resin, which is an open cell material. The sound absorbing layer 24 is arranged to reduce a sound coming from inside the noise reduction case 10 and provide soundproofing for the transmission 102. In particular, the sound absorbing layer 24 is configured to absorb soundwaves coming from the transmission 102.
The noise reduction cladding 20 further comprises a pyramidal surface pattern 26. The pyramidal surface pattern 26 is arranged on the sound absorbing layer 24 on a side opposite to the sound reflecting layer 22. In the embodiment shown here it is composed of the same material as the sound absorbing layer 24, but it could be composed of the same material as the sound reflecting layer 22. Additionally or alternatively, it could also comprise further materials. The pyramidal surface pattern 26 comprises a plurality of pyramids arranged on the surface of the sound absorbing layer 24 in a grid pattern. They are configured to further improve the noise insulation of the noise reduction case 10, for example by reflecting, absorbing, or breaking up soundwaves.
The displacement section 30 is formed by an extension of the noise reduction cladding 20 beyond the extent of the structural frame 12, and comprises the sound reflecting layer 22, the sound absorbing layer 24 and the pyramidal pattern 26. It has a height of approximately 50 mm. The displacement section 30 is configured to be in contact with an engine bed 104 and remain in contact with it throughout an operation of the propulsion unit 100. The transmission 102 may experience a displacement during operation of the propulsion unit 100. The displacement section 30 is therefore configured to deform in response to this displacement to maintain contact with the engine bed 104. The displacement section 30 provides a distancing between the structural frame 12 and the engine bed 104. It thus prevents a collision of these components during operation of the propulsion unit 100, preventing damage to the structural frame 12. The displacement section 30 also provides further noise reduction by reducing the amount of sound exiting from the transmission 102. Additionally, the displacement section 30 provides a dampening of the movement of the transmission 102, thereby further reducing noise and absorbing vibrations.
Fig. 3 schematically shows the noise reduction case 10 mounted on the propulsion unit 100 of Fig. 1. The propulsion unit 100 comprises an electric motor 112, the transmission 102, and a propeller 106. The electric motor 112 is mechanically connected to the transmission 102 via torsional dampers 114 and a shaft 118. The transmission 102 is further mechanically connected to the propeller 106 via two shafts 110 arranged at 90° to each other, which are mechanically connected to each other via bevel gears 108. The electric motor 112 can therefore transmit a torque to the propeller 106 via the transmission 102. The transmission 102 is arranged above the engine bed 104 of the watercraft 200, through which one of the shafts 110 passes. The transmission 102 is encased in the noise reduction case 10, which is supported on the engine bed 104 via the displacement section 30.
The transmission 102 comprises a bell housing, which is not shown here. The transmission 102 and its bell housing experience a displacement of up to 10 mm during operation, in particular along a vertical direction. This results in a maximum distance between the highest and lowest point of up to 20 mm. In the embodiment shown in fig. 3, the noise reduction case 10 is fixedly attached to the bell housing of the transmission 102 and therefore moves with it. The noise reduction case 10 is fixed to the bell housing via a transmission coupling device 116, which is indicated here with two crosses. The transmission coupling device 116 may comprise a metal plate and at least four screws. To prevent a collision of the rigid structural frame 12 and the engine bed 104, the displacement section 30 is configured to deform and compress in response to the displacement during operation described above. It further maintains contact with the engine bed 104, providing a noise reduction and absorbing vibrations of the transmission 102. This also provides a degree of mechanical and acoustic isolation between the transmission 102 and the engine bed 104 and therefore the rest of the watercraft 200.
Fig. 4 schematically shows an alternative mounting of the noise reduction case 10 to the propulsion unit 100. The propulsion unit 100 is the same as shown in fig. 3. As the noise reduction case 10 and its mounting are similar to the one shown in fig. 3, only the differences to it will be described in relation to fig. 4. The noise reduction case 10 is still arranged around the transmission 102, however, it is fixed to the engine bed 104 via a bed coupling device, provided here by brackets 32. It is therefore not fixed to the bell housing of the transmission 102. The brackets 32 are attached to the engine bed 104 via screws, which are not shown here.
In the embodiment of fig. 4, the noise reduction case 10 comprises an additional displacement section 34, which is indicated by a rectangle arranged around the shaft 118 of the transmission 102 and inside the noise reduction case 10. This additional displacement section 34 has the function of preventing a collision between the transmission 102 and the noise reduction case 10, in particular the structural frame 12. The additional displacement section 34 is in contact with the bell housing of the transmission 102. Like the displacement section 30, it is configured to compress and deform in response to a movement of the transmission 102 within the noise reduction case 10. In particular, it is configured to prevent a collision between the bell housing and the structural frame 12 to prevent damage, to absorb vibrations and to reduce a noise.
Fig. 5 schematically shows a method for mounting the noise reduction case 10 on the propulsion unit 100 as shown in fig. 3. The method shown comprises a first step I of positioning the noise reduction case 10 over the transmission 102 of the propulsion unit 100. In an embodiment, the noise reduction case 10 comprises a lower and an upper part which can be coupled together. In this case, the lower part may be positioned first around the transmission 102, and the upper part may be coupled to the lower part at a later point.
The method also comprises a step II of compressing the displacement section 30 against the engine bed 104. This is done by applying a force to the noise reduction case 10. This step can comprise the use of a precompression template, which is a device for compressing the displacement section 30 up to a predefined height above the engine bed 104. This enables a precise and controlled compression of the displacement section 30 to a desired initial position. The displacement section 30 can thus be precisely tuned to the expected displacement of the propulsion unit 100.
The method also comprises a step III of coupling the structural frame 12 of the noise reduction case 10 to the transmission 102 of the propulsion unit 100. More precisely, it comprises coupling the structural frame 12 to the bell housing of the transmission 102. This can be done through the transmission coupling device 116, which may fix the structural frame 12 to the bell housing through the use of screws. The screws may be inserted from the transmission side but may also be inserted from another side.
The method further comprises a step of removing the load from the noise reduction case 10, that is, stop applying a force to the noise reduction case 10. As the noise reduction case 10 is coupled to the transmission 102, it will not move after the load is removed, and the displacement section 30 will remain compressed to a desired amount. The method may further comprise a step of attaching the upper part of the noise reduction case 10 to the lower part.
In an alternative embodiment of the method, which may be used for mounting the noise reduction case 10 on the propulsion unit 100 as shown in fig. 4, the steps may be analogous. A difference may be that the displacement section 30 is compressed against the transmission 102, in particular against the bell housing of the transmission 102, instead of the engine bed 104. A further difference may be that the noise reduction case is coupled to the engine bed 104 instead of the transmission 102, which may be done through brackets 32.

Reference signs

10: noise reduction case
12: structural frame
20: noise reduction cladding
22: sound reflecting layer
24: sound absorbing layer
26: pyramidal pattern
28: acrylic adhesive
30: displacement section
32: bracket
34: additional displacement section
100: propulsion unit
102: transmission
104: engine bed
106: propeller
108: gear
110: shaft
112: motor
114: torsional damper
116: transmission coupling device
118: shaft
200: watercraft

Claims

A noise reduction case (10) for a transmission (102) of a propulsion unit (100) of a watercraft (200), the propulsion unit (100) comprising a motor (112) for driving a propeller (106) via the transmission (102) and an engine bed (104) for supporting the motor (112), comprising a structural frame (12) mechanically couplable to the propulsion unit (100), and a noise reduction cladding (20) arranged on the structural frame (12) for reducing a noise of the transmission (102), wherein the noise reduction cladding (20) comprises a displacement section (30; 34) configured to deform in response to a relative movement between the transmission (102) and the engine bed (104) of the propulsion unit (100).
The noise reduction case (10) according to claim 1, characterized in that the noise reduction case (10) comprises a transmission coupling device (116) configured to enable a coupling of the noise reduction case (10) to the transmission (112), and in that the displacement section (30) is configured to maintain a contact between the noise reduction case (10) and the engine bed (104) during the relative movement.
The noise reduction case (10) according to claim 1, characterized in that the noise reduction case (10) comprises a bed coupling device (32) configured to enable a coupling of the noise reduction case (10) to the engine bed (104), and in that the displacement section (34) is configured to maintain a contact between the noise reduction case (10) and the transmission (102) during the relative movement.
The noise reduction case (10) according to one of the preceding claims, characterized in that the noise reduction cladding (20) comprises a sound reflecting layer (22).
The noise reduction case (10) according to claim 4, characterized in that the sound reflecting layer (22) comprises a closed cell material.
The noise reduction case (10) according to one of the claims 4 and 5, characterized in that the sound reflecting layer (22) comprises a thickness between 30 mm and 60 mm.
The noise reduction case (10) according to one of the preceding claims, characterized in that the noise reduction cladding (20) comprises a sound absorbing layer (24).
The noise reduction case (10) according to claim 7, characterized in that the sound absorbing layer (24) comprises an open cell material.
The noise reduction case (10) according to one of the claims 7 and 8, characterized in that the sound absorbing layer (24) comprises a thickness between 20 mm and 50 mm.
The noise reduction case (10) according to one of the preceding claims, characterized in that the noise reduction cladding (20) comprises a pyramidal surface pattern (26).
The noise reduction case (10) according to one of the preceding claims, characterized in that the displacement section (30; 34) comprises a thickness between 40 mm and 60 mm.
A method for mounting a noise reduction case (10) according to one of the preceding claims to a propulsion unit (100) of a watercraft (200), the propulsion unit (100) comprising a motor (112) for driving a propeller (106) via a transmission (112) and an engine bed (104) for supporting the motor (112), comprising the steps of positioning (I) the noise reduction case (10) over the transmission (102), compressing (II) the displacement section (30) against the propulsion unit (102; 104) by applying a force to the noise reduction case (10), and mechanically coupling (III) the structural frame (12) to the propulsion unit (100) with the displacement section (30) being in a compressed state.
A propulsion unit (100) for a watercraft (200), the propulsion unit (100) comprising a motor (112) for driving a propeller (106) via a transmission (102) and an engine bed (104) for supporting the motor (112), comprising a noise reduction case (10) according to one of the claims 1 to 11, wherein the structural frame (12) of the noise reduction case (10) is mechanically coupled to the transmission (102) and the displacement section (30) is in contact with the engine bed (104) of the propulsion unit (100).
A propulsion unit (100) for a watercraft (200), the propulsion unit (100) comprising a motor (112) for driving a propeller (106) via a transmission (102) and an engine bed (104) for supporting the motor (112), comprising a noise reduction case (10) according to one of the claims 1 to 11, wherein the structural frame (12) of the noise reduction case (12) is mechanically coupled to the engine bed (104) of the propulsion unit (100) and the displacement section (34) is in contact with the transmission (102) of the propulsion unit (100).
A watercraft (200) with a propulsion unit (100) according to one of claims 13 and 14.