Improved outboard motor unit

Abstract

 An outboard motor unit comprising a containment casing (4) housing in its interior a motor (10), disposed with its axis at an angle to the rotation shaft (32) of a propeller (24), and operatively connected to this latter by transmission means (22, 36, 36'), the lower portion (16) of said containment casing housing said propeller and being of tapering profile, wherein inside said containment casing, a cooling circuit is provided for said motor, comprising:
- an aperture (30) for the entry, into said circuit, of the water in which the motor unit is immersed, said aperture being defined at the tip of the tapering profile of said lower portion and axially facing and aligned with said shaft of the propeller;
- an impeller (40) connected directly to said shaft of the propeller such that said rotation shaft of said propeller coincides with, and is aligned with, that of said impeller, and acting in the sense of feeding the water which has entered said circuit to a delivery conduit for cooling said motor;
- at least one aperture for the exit of the water after it has cooled said motor.

Description

[0001] The present invention relates to an improved outboard motor unit.

[0002] Motors for watercraft include outboard motors, so-called because the motor unit is mounted at the craft stern board, and remains suspended outside its hull.

[0003] Traditionally, the motor unit is housed within a single cover block or cowling of plastic or metal construction. The actual motor, which can be of internal combustion engine type (petrol or diesel) or electric type, is positioned in the top of the cover block and is mechanically connected to the propeller which is positioned in the bottom of the cover block, which is immersed in water and provided with a vertically projecting fin.

[0004] Currently, motor units of small cylinder capacity are known, which are housed within the cover block at a lower level than the hull waterline, and to which the motor unit is applied. These motor units do not require a cooling system, as heat exchange takes place directly between the walls of the cavity of the block housing the motor unit and the water, in which the motor unit is immersed.

[0005] Motor units, both of electric and internal combustion engine type, used in particular for planing boats are also known, in which the motor is usually of large cylinder capacity. These motor units require a cooling circuit, which comprises a pump for withdrawing water from around the motor unit and transfers it into a cooling circuit which feeds it to the motor.

[0006] Traditionally, the pump which transfers the water to the cooling circuit is positioned in the central portion of the cover block, i.e. in the zone which houses the vertical transmission shaft and which lies between motor positioned upperly and the propeller positioned lowerly.

[0007] However, some known motor units which use an electric motor and require a cooling system, have a cover block with a central portion of such dimensions as not to offer sufficient space for housing the impeller of the cooling system pump.

[0008] US 3025824 describes a motor unit with a cooling system in which the containment casing lowerly presents a body of tapering profile; the inlet water to the impeller of the cooling circuit enters through an aperture defined in said tapering body in a position out of alignment with the axis passing through the body tip. Moreover, the propeller shaft and the impeller shaft are not connected directly together; in particular, the motor shaft is connected to the propeller shaft via a first gear, and to the impeller shaft via a second gear. This motor unit is rather complicated to produce and hence costly.

[0009] US 4832635 does not describe an outboard motor unit, but specifically relates to the construction of the conical nose portion of a marine engine to be installed on ships of large dimensions. Specifically, because of the large spaces available in this type of craft, the engine is disposed horizontally with respect to the propeller axis, and the cooling system does not comprise an impeller, as it would not be able to provide a sufficient intake force for the water.

[0010] The main object of the invention is to propose an improved motor unit able to eliminate the drawbacks of the traditional solutions.

[0011] Anther object of the invention is to propose an improved motor unit having a cooling system more efficient than traditional systems.

[0012] Anther object of the invention is to propose an outboard motor unit of simple, quick and low-cost construction.

[0013] All these objects and others which will be apparent from the ensuing description are attained, according to the invention, by an improved motor unit with the characteristics indicated in claim 1.

[0014] A preferred embodiment of the present invention is further clarified hereinafter with reference to the accompanying drawings, in which:

Figure 1

is a perspective view of a part of the foot of the improved motor unit according to the invention,

Figure 2

is a vertical section through that portion of the foot positioned below the hull waterline.

[0015] As can be seen from the figures, the motor unit according to the invention comprises a containment structure, composed of an upper cover, not shown, which is always positioned above the hull waterline, and an underlying containment casing defining the foot 4.

[0016] In greater detail, the upper portion 6 of the foot 4 has a shape which extends horizontally in the longitudinal direction to define a front cylindrical cavity 8 for housing an electric motor 10, and a rear compartment 12 for housing an electronic card 14 for its control. The motor 10 is of vertical axis, with its operation controlled by the electronic card 14. In this case, the upper cover of the motor unit houses the powering batteries, preferably of lithium type, which are rechargeable by connection to a normal electric socket; in addition, the interior of the cover can also house supplementary batteries and a battery charger.

[0017] The motor 10 can also be of internal combustion engine type and be housed inside the upper cover of the motor unit, to hence be positioned completely above the hull waterline. Alternatively, the motor 10 can be disposed inside the upper portion 6 of the foot 4 in such a manner that a part thereof is located at a lower level than the hull waterline.

[0018] The electronic card 14 is positioned within the containment structure at a level below the hull waterline.

[0019] Advantageously, the front cylindrical cavity 8 housing the electric motor 10 and/or the rear compartment 12 housing the electronic card 14 are located in proximity to those outer walls of the containment structure which are in contact with the water in which the hull is immersed; in greater detail, the cavity 8 and/or the rear compartment 12 are disposed within the containment structure such that heat exchanges takes place directly between these and the water which grazes the outer walls of the containment structure; this enables the electronic card 14 to be cooled and, moreover, can also advantageously contribute to the cooling of the motor 10.

[0020] The upper portion 6 of the foot 4 is connected to the lower portion 16 thereof by a connection portion 18 which extends vertically and has a limited width in the transverse direction. Inside this connection portion 18 a chamber 20 is defined housing a shaft 22 for transmitting motion from the motor 10 to a propeller 24.

[0021] The propeller 24 is mounted and housed in the lower portion 16 of the foot 4. The lower portion 16 is of tapering profile, preferably nose-shaped, to enable optimal fluidodynamic penetration into water.

[0022] The lower portion 16 also presents a through aperture 30 at the tip of the tapering profile (see Figure 1). In particular, the through aperture 30 is aligned with the axis 31 passing centrally through the tapering profile of the lower portion 16 and about which the tapering outer surface of the lower portion 16 develops by rotation.

[0023] Preferably, the lower portion 16 comprises an internally hollow tapering structure of substantially horizontal axis. In particular, this structure connects at its rear to a cylindrical portion 26, while at its front it connects to a nose-shaped cap 28 provided with the through aperture 30. In particular, the cap 28 is removable to provide easy quick access to the components housed within the lower portion 16, for carrying out maintenance operations.

[0024] The rotation shaft 32 of the propeller 24, with relative support bearings 34, is inserted through the lower portion 16. The shaft 32 of the propeller 24 is mechanically connected to the transmission shaft 22 via a pair of bevel gears 36, 36', housed in a chamber 38 provided in the lower portion 16.

[0025] Both the chamber 20 and the chamber 38 are completely isolated from the outside and are filled with oil, such that the shaft 22 and the bevel gears 36, 36' are able to work with very low friction and virtually without requiring maintenance.

[0026] The front end of the propeller shaft 32 is directly connected to, and rigidly associated with, an impeller 40. In particular, the rotation shaft 32 of the propeller is aligned with and coincides with the rotation shaft of the impeller 40.

[0027] The impeller 40 acts on the water which, via the through aperture 30, enters a channel 42, defined preferably within the shaped cap 28.

[0028] In particular, the shaft 32 of the propeller 24 and of the impeller 40 is aligned with the through aperture 30, with the water inlet channel 42, and with the axis of rotation 31 about which the tapering profile of the lower portion 16 develops, and in which said shaft 32 is housed.

[0029] Behind the impeller 40, a shield 44 is provided for closing the hydraulic part and for isolating it from the chamber 38 containing the bevel gears 36, 36'.

[0030] A vertical conduit 46 extends radially from the top of the chamber housing the impeller 40, and passes through the connection portion 18 to feed the water originating from the impeller 40 into an annular chamber 48 of vertical axis, which surrounds a large part of the cylindrical cavity 8 housing the electric motor 10. This annular chamber 48 is also provided with a hole or conduits, not shown, for discharging the water to the outside after it has exchanged heat with the motor 10.

[0031] Essentially, inside the foot 4, a cooling circuit is defined for the motor 10 into which the water, in which the motor unit is immersed, enters (in particular through suitable conduits present in the containment casing) via the aperture 30. The impeller 40 then acts such as to feed the water, which has enters the circuit, to a delivery conduit for cooling the motor 10. Subsequently, after cooling the motor 10, the water leaves to the outside of the foot 4 from another through aperture, not shown.

[0032] If a motor of internal combustion engine type is used, the water originating from the impeller 40 is fed into a suitable motor cooling circuit, comprising a heat exchanger.

[0033] The lower portion 16 of the foot 4 extends downwards into a vertical fin 50, which enables the motor unit to be suitably used as a rudder.

[0034] From the aforegoing, it is apparent that the motor unit according to the invention is much more advantageous than traditional units, and in particular:

• by virtue of the direct mechanical connection between the impeller of the cooling system pump and the propeller rotation shaft, no intervention is required on the system for transmitting motion from the motor to the propeller, hence enabling the construction of the motor unit to be considerably simplified,
• the seat for housing the impeller can be formed by casting during the formation of the body of the foot, with substantial production cost reduction,
• the fact that the cooling system water inlet always lies below the waterline enables the system to be easily and immediately activated once the motor unit has been positioned in the water; moreover, this cooling system is also more efficient in that the pressure due to advancement of the hull is added to the suction effect of the pump impeller,
• the fact that the water inlet aperture and conduit are aligned with the propeller and impeller shaft, and in particular are aligned with the axis of rotation about which of the tapering body of the lower portion develops, ensures optimal fluorodynamic penetration in water and in addition simplifies both the construction of the components and their assembly,
• it is usable virtually for all motor types, both of electric and internal combustion engine type.

[0035] In particular, in contrast to US 3015824, in the present invention, the water entry aperture and conduit leading to the impeller, the impeller rotation shaft, the propeller shaft and the axis of rotation about which the tapering body of the lower portion develops, are all mutually aligned. This specific configuration enables improved hydrodynamic behaviour; in particular, by positioning the aperture at the tip of the tapering body, the water is drawn into the cooling system, with consequent nullification of the stagnation point and the overpressure usually present at said point.

[0036] In addition, this enables a greater water flow to enter the cooling system; in particular, on increasing the advancement velocity of the craft, the water flow entering the cooling system also increases, due both to the suction effect of the impeller, and the particular hydrodynamic effect of the absence of a stagnation point at the tip of the tapering body. In this manner, for equal liquid handled, the primary energy absorbed by the impeller is reduced.

[0037] Moreover, according to the present invention, the impeller is connected directly to the front end of the propeller shaft, while in US 3015824 the propeller shaft and impeller shaft are not connected together directly, but via the motor rotation shaft. This makes the present invention simpler to implement and assemble, and hence less costly, and in addition leads to greater efficiency of motion transmission between the motor shaft and the propeller and impeller shaft.

Claims

1. An improved outboard motor unit comprising a containment casing (4) housing in its interior a motor (10), disposed with its axis at an angle to the rotation shaft (32) of a propeller (24), and operatively connected to this latter by transmission means (22, 36, 36'), the lower portion (16) of said containment casing (4) housing said propeller (24) and being of tapering profile, characterised in that, inside said containment casing (4), a cooling circuit is provided for said motor (10), comprising:

- an aperture (30) for the entry, into said circuit, of the water in which the motor unit is immersed, said aperture being defined at the tip of the tapering profile of said lower portion (16) and axially facing and aligned with said shaft (32) of the propeller (24);

- an impeller (40) connected directly to said shaft (32) of the propeller (24) such that said rotation shaft (32) of said propeller (24) coincides with, and is aligned with, that of said impeller (40), and acting in the sense of feeding the water which has entered said circuit to a delivery conduit for cooling said motor (10);

- at least one aperture for the exit of the water after it has cooled said motor (10).

2. A motor unit as claimed in claim 1, characterised in that the axis of said motor (10) is vertical and is disposed perpendicular to the shaft (32) of said propeller (24).

3. A motor unit as claimed in one or more of the preceding claims, characterised in that said lower portion (16) is defined by a channel (42) for water passage, said channel (42) being interposed between said aperture (30) and said impeller (40), and being aligned both with said aperture (30) and with the shaft (32) of the propeller and of the impeller (40).

4. A motor unit as claimed in one or more of the preceding claims, characterised in that the aperture (30) for water entry into the cooling circuit and said water passage channel (42) are provided in a nose-shaped removable holed element (28).

5. A motor unit as claimed in one or more of the preceding claims, characterised by comprising an electronic card (14) for controlling said motor (10), said electronic card (14) being housed in said containment casing (4) at a lower level than the waterline of the hull to which said motor unit is applied.

6. A motor unit as claimed in one or more of the preceding claims, characterised in that said motor (10) is of internal combustion engine type or electric type.

7. A motor unit as claimed in one or more of the preceding claims, characterised in that in said containment casing (4), the zones (8, 12) housing the electric motor (10) and electronic card (14) are disposed within said containment casing (4) such as to enable direct heat exchange between said zones (8, 12) and the water in contact with the outer walls of said casing.

8. A motor unit as claimed in one or more of the preceding claims, characterised in that said transmission means (22, 36, 36') are housed in an oil-filled chamber (20, 38) defined inside said containment casing (4).

9. A motor unit as claimed in one or more of the preceding claims, characterised in that said transmission means comprise a bevel gear pair (36, 36') interposed between said motor (10) and said propeller (24).

10. A motor unit as claimed in one or more of the preceding claims, characterised in that said delivery conduit (46) feeds water to a chamber (48) which at least partially wraps said motor (10).

11. A motor unit as claimed in one or more of the preceding claims, characterised in that said lower portion (16) is of nose-shape.

12. A motor unit as claimed in one or more of the preceding claims, characterised in that said through aperture (30) is aligned with the axis (31) passing through the centre of the tapering profile of said lower portion (16) and about which the outer surface of said lower portion (16) develops by rotation.

13. A motor unit as claimed in one or more of the preceding claims, characterised in that said motor (10) is disposed inside said containment casing (4) in such a manner as to lie totally at a level lower than the waterline of the hull to which said motor is applied.

14. A motor unit as claimed in one or more of claims from 1 to 13, characterised in that at least a part of the motor (10) is positioned at a level higher than the waterline of the hull to which the motor unit is applied.

15. A motor unit as claimed in one or more of the preceding claims, characterised in that said cooling circuit comprises a heat exchanger which wraps said motor (10).

Drawing