MARINE DRIVE UNIT WITH A COOLING OIL CIRCUIT

Abstract

The present invention relates to a marine drive unit (1) comprising an upper bevel gear set (2) and a lower bevel gear set (3). The upper bevel gear set (2) is connected to the lower bevel gear set (3) by a drive shaft (4) which extends in vertical direction. A first oil pump (5) is arranged to supply oil to the upper bevel gear set (2) and a second oil pump (6) is arranged to feed a cooling oil circuit.

Claims

1. A marine drive unit (1) comprising: an upper bevel gear set (2); a lower bevel gear set (3); a drive shaft extending in a vertical direction and connecting the upper bevel gear set (2) to the lower bevel gear set (3); a first oil pump (5) arranged to supply oil to the upper bevel gear set (2); and a second oil pump (6) arranged to feed a cooling oil circuit.

2. The marine drive unit according to claim 1, comprising: at least one pressure operated clutch (7, 8) configured to reverse a rotational direction of the drive shaft (4) with regard to an input shaft (9) of the marine drive unit (1); and wherein the first oil pump (5) is arranged to supply pressure for the pressure operated clutch (7, 8).

3. The marine drive unit according to claim 1, wherein the second oil pump (6) is located at a lower end (10) of the drive shaft (4) and defines at least one first opening (13), the second oil pump configured to suck oil from an oil reservoir (11) through a bore (12) in the drive shaft (4) and to pump it through the at least one first opening (13) at the second oil pump (6) back to the oil reservoir (11).

4. The marine drive unit according to claim 1, wherein the second oil pump (6) is located at a lower end (10) of the drive shaft (4) and defining at least one first opening (13) and at least one second opening (17), the second oil pump configured to suck oil from an oil reservoir (11) through the at least one first opening (13) at the second oil pump (6) and to pump it through a bore (12) in the drive shaft (4) and through the at least one second opening (17) back to the oil reservoir (11).

5. The marine drive unit according to claim 3, comprising an underwater housing defining an inside space, wherein the drive shaft (4) is arranged at least partially inside the underwater housing (14) and wherein the inside space of the underwater housing (14) forms the oil reservoir (11).

6. The marine drive unit according to claim 4, wherein the drive shaft (4) comprises an upper shaft section (15) and a lower shaft section (16), wherein the bore (12) in the drive shaft is a central bore in the lower shaft section (16), and wherein the at least one second opening (17) is between the oil reservoir (11) and the bore (12) and is further positioned between the upper and lower shaft section (15, 16).

7. The marine drive unit according to claim 6, further comprising a sleeve (18) connecting the upper shaft section (15) to the lower shaft section (16), and wherein the at least one second opening (17) is arranged at the sleeve (18).

8. The marine drive unit according to ene of the preceding claim 1, wherein the second oil pump (6) comprises a pump screw (19) which is arranged co-axially to the bore (12) in the drive shaft (4).

9. The marine drive unit according to claim 8, wherein the pump screw (19) extends at least partially inside the drive shaft (4).

10. The marine drive unit according to claim 1, wherein the second oil pump (6) is driven via the drive shaft (4) and a pair of pump gears (20, 21).

11. The marine drive unit according to claim 2, wherein the second oil pump (6) is located at a lower end (10) of the drive shaft (4) and defines at least one first opening (13), the second oil pump configured to suck oil from an oil reservoir (11) through a bore (12) in the drive shaft (4) and to pump it through the at least one first opening (13) at the second oil pump (6) back to the oil reservoir (11).

12. The marine drive unit according to claim 2, wherein the second oil pump (6) is located at a lower end (10) of the drive shaft (4) and defining at least one first opening (13) and at least one second opening (17) between the oil reservoir and the bore, the second oil pump configured to suck oil from an oil reservoir (11) through the at least one first opening (13) at the second oil pump (6) and to pump it through a bore (12) in the drive shaft (4) and through the at least one second opening (17) back to the oil reservoir (11).

13. The marine drive unit according to claim 12, wherein the second oil pump (6) comprises a pump screw (19) arranged co-axially with the bore (12) and extending at least partially inside the drive shaft (4).

14. The marine drive unit according to claim 12, comprising an underwater housing, wherein the drive shaft (4) is arranged at least partially inside the underwater housing (14) and wherein an inside space of the underwater housing (14) forms the oil reservoir (11).

15. The marine drive unit according to claim 14, wherein the drive shaft (4) comprises an upper shaft section (15) and a lower shaft section (16), wherein the bore (12) in the drive shaft is a central bore in the lower shaft section (16), and wherein the at least one second opening (17) is between the upper and lower shaft section (15, 16).

16. The marine drive unit according to claim 15, further comprising a sleeve (18) connecting the upper shaft section (15) to the lower shaft section (16), and wherein the at least one second opening (17) is arranged at the sleeve (18).

17. The marine drive unit according to claim 16, wherein the second oil pump (6) comprises a pump screw (19) arranged co-axially with the bore (12) and extending at least partially inside the drive shaft (4).

18. The marine drive unit according to claim 17, wherein the second oil pump (6) is driven via the drive shaft (4) and a pair of pump gears (20, 21).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will be further and more particularly described in the following, by way of example only, and with reference to the accompanying figures.

[0021] FIG. 1 shows a marine drive unit according to the invention in a schematic drawing,

[0022] FIG. 2 shows a section of a further embodiment of a marine drive unit according to the invention, and

[0023] FIG. 3 shows a screw pump as used in the marine drive unit of FIG. 2.

DETAILED DESCRIPTION

[0024] A marine drive unit 1 as shown in FIG. 1 is driven by an engine 22, for example an internal combustion engine, which is located inside the hull 23 of a boat. The output shaft 24 of the engine 22 is coupled to an input shaft 9 of the marine drive unit 1. In this embodiment a joint shaft is coupled between the output shaft 24 and the input shaft 9. Input shaft 9 enters a upper housing 25 of an upper bevel gear set 2. The engine 22 and the upper housing 25 of the upper bevel gear set 2 are fastened to the hull 23 or to structural parts inside of the hull 23.

[0025] In the upper housing 25 there are a forward clutch 7 and a backward clutch 8 in the form of multi-disk-clutches provided to reverse the rotational direction of a drive shaft 4 with regard to the input shaft 9. The upper bevel gear set 2 connects the input shaft 9 to a vertically arranged drive shaft 4 and a lower bevel gear set 3 connects the drive shaft 4 to a horizontally arranged propeller shaft 26. A propeller 27 is rigidly fixed to the propeller shaft 26. The lower bevel gear set 3 and the propeller shaft 26 are supported in an underwater housing 14 which protrudes from the bottom of the hull 23 into the water. The underwater housing 14 can be rotated about a vertical rotation axis to adjust the steering direction of the propeller thrust and to steer the boat in the desired direction.

[0026] A first oil pump 5 is mounted in the upper housing 25 and driven by the input shaft 9. The first oil pump 5 delivers oil to the upper bevel gear set 2 for cooling and lubrication. Said first oil pump 5 supplies pressure for the hydraulic operation of the forward/reverse-clutches 7 and 8 which are provided to reverse the rotational direction of the drive shaft 4 with regard to the input shaft 9. Said first oil pump 5 sucks oil from an oil reservoir 11 inside the underwater housing 14.

[0027] Additionally, a second oil pump 6 is arranged at the lower end 10 of the drive shaft 4 to suck oil from the upper part of said oil reservoir 11 through a bore 12 inside the drive shaft 4 and to pump the oil into the lower part of the underwater housing 14. Thus, a cooling oil circuit is provided additionally to the pressure oil circuit effected by the first oil pump 5. Both said oil circuits can be operated with the same oil. Both said oil circuits are using the same oil reservoir 11.

[0028] The drive shaft 4 comprises an upper shaft section 15 and a lower shaft section 16 which are coupled with each other by means of a sleeve 18. The sleeve 18 has got several second openings 17 around its circumference. The oil level 33 in the underwater housing 14 is higher than the second openings 17 in the sleeve 18, so that oil can flow into the sleeve 18 and through a bore 12 in the lower shaft section 16 to the second oil pump 6 at the lower end 10 of the drive shaft 4.

[0029] FIG. 2 shows a sectional view of the lower part of another embodiment of a marine drive unit. The same components of the marine drive unit in FIG. 2 are indicated with the same referrals as in FIG. 1. The main difference of FIG. 2 are the two contra-rotating propellers 27 and 28 instead of the single propeller in FIG. 1. In this case the lower bevel gear set 3 comprises one driving bevel gear and two driven bevel gears. A first driven bevel gear is coupled by a hollow propeller shaft 29 to the first propeller 27 and a second driven bevel gear is coupled by the inner propeller shaft 30 to the second propeller 28.

[0030] The underwater housing 14 is fixed to a hollow steering shaft 31 which is rotatably supported in the hull 23 with roller bearing 32, so that the underwater housing 14 together with the propeller shafts 29 and 30 is rotatable about a vertical rotational axis 34.

[0031] A lower shaft section 16 of the drive shaft 4 is arranged with its greater part inside the underwater housing 14 of the marine drive unit 1. The inside space of the underwater housing 14 forms the oil reservoir 11. Therefor the underwater housing 14 is filled with oil. The oil reaches up into the steering shaft 31. The oil level 33 is higher than a sleeve 18, which couples the lower shaft section 16 to the upper shaft section 15 of the vertical drive shaft 4.

[0032] The second oil pump 6 is located at the lower end 10 of the drive shaft 4. The drive shaft 4 is coaxial to the rotational axis 34. The bore 12 extends from the upper end of the lower shaft section 16 to its lower end. The bore 12 is coaxial to the rotational axis 34. Several second openings 17 in the sleeve 18 are used as oil intakes into the bore 12, as the second oil pump 6 sucks oil from the oil reservoir 11 through the second openings 17 and the bore 12 to the lower end of the drive shaft 14. At the lower end 10 of the drive shaft 4 the second oil pump 6 pumps the oil through first openings 13 back into the oil reservoir 11. Thus, a cooling oil circuit is effected. There are two first openings 13 located near the lower end of a screw pump jacket 35.

[0033] In another embodiment of the invention, the direction of oil flow in the cooling oil circuit may be reversed. In such an embodiment the first openings 13 can be used as intakes for the oil. The oil will be pumped from the first openings 13 at the lower end 10 of the drive shaft 4 through the bore 12 upwards to second openings 17 in the drive shaft 4 and back into the oil reservoir 11.

[0034] The second oil pump 6 is shown in further detail in FIG. 3. The second oil pump 6 is a screw type pump. A pump screw 19 is arranged in a pump jacket 35 which can be fastened to the lower end 10 of the drive shaft 4. This way, the pump jacket 35 will rotate together with the drive shaft 4. The pump screw 19 will rotate with a different speed, depending on the gear ratio of a pair of pump gears 20 and 21, which drive the pump screw 19 as described below. An outer cylindrical surface of the pump screw 19 is dimensioned to fit into an inner cylindrical surface of the screw pump jacket 35. A collar 38 is arranged at the outside of the pump jacket 35. The collar 38 comprises screw holes 39, 40 for fastening the pump jacket 35 to the lower end 10 of the drive shaft 4.

[0035] The pump jacket 35 with the pump screw 19 extends partially inside the drive shaft 4 at its lower end 10. A cover 36 is fixed to the upper end of the pump jacket 35. Several orifices 37 in the cover 36 connect the inner space of the pump jacket 35 to the bore 2. A driving stud 41 of the pump screw 19 protrudes from the lower end of the pump jacket 35. A driven pump gear 21 is fixed to the driving stud 41. The driven pump gear 21 meshes with a driving pump gear 20. The driving pump gear 20 is manufactured together with a bevel gear wheel of the lower bevel gear set 3 from one piece. The pair of pump gears 20 and 21 can be modified to change the gear ratio. Thereby optimizing the volume of oil exchanged in the cooling oil circuit.

REFERENCES

[0036] 1 marine drive unit [0037] 2 upper bevel gear set [0038] 3 lower bevel gear set [0039] 4 drive shaft [0040] 5 first oil pump [0041] 6 second oil pump [0042] 7 clutch [0043] 8 clutch [0044] 9 input shaft [0045] 10 lower end [0046] 11 oil reservoir [0047] 12 bore [0048] 13 first opening [0049] 14 underwater housing [0050] 15 upper shaft section [0051] 16 lower shaft section [0052] 17 second opening [0053] 18 sleeve [0054] 19 pump screw [0055] 20 pump gear [0056] 21 pump gear [0057] 22 engine [0058] 23 hull [0059] 24 output shaft [0060] 25 upper housing [0061] 26 propeller shaft [0062] 27 propeller [0063] 28 propeller [0064] 29 hollow propeller shaft [0065] 30 inner propeller shaft [0066] 31 steering shaft [0067] 32 roller bearing [0068] 33 oil level [0069] 34 rotational axis [0070] 35 pump jacket [0071] 36 cover [0072] 37 orifice [0073] 38 collar [0074] 39 screw hole [0075] 40 screw hole [0076] 41 driving stud