AU3697589A - Engine and gearbox assemblies - Google Patents

Description

Engine and Gearbox Assemblies

The present invention relates to internal coπibustion engine and gearbox asseπiblies for driving a load.

In many cases, the rotational speed range of an internal ocnibustion engine output shaft in which the engine develops optimum performance in terms of power output and economy does not coincide with the optimum speed at which a load, such as a centrifugal pump or an electrical generator, is to be driven. Accordingly, a gearbox, which often is of fixed ratio, has to be inserted between the engine and the load to match the optimum operating speeds of both engine and load.

According to the present invention there is provided an engine and gearbox assembly comprising an internal coπibustion engine having an output shaft and a pressurised lubrication system including a passage in the output shaft, and a speed-changing gearbox an input element of which is drivably connected to the crankshaft, wherein a pressurised lubricant supply duct in the crankshaft extends axially from the said passage.through a substantially pressure-tight bearing into a further passage in an element of the gearbox which is coaxial with the crankshaft, the said further passage forming part of a pressurised lubricant supply system for the gearbox from which lubricant can return to the engine sump.

Such an arrangement enables all the journal bearings in the gearbox to be pressure-lubricated, without the need for an additional oil- puπp. This is particularly advantageous where the gear box is of the planetary type, such as an epicyclic gearbox, in which case the planet pinion bearings can be supplied with lubricant under pressure through supply passages in the planet carrier (whether fixed or rotating), themselves supplied from the said further passage.

Where the planet carrier is to be fixed to the engine output shaft for rotation therewith, it is conveniently formed with lubrication passages for supplying the planet pinion bearings with lubricant under pressure from the duct in the output shaft while the bearings for the sun or ring gear of the epicyclic gearbox are supplied under pressure through the said bearing which locates the sun gear or ring gear relative to the engine output shaft..

Embodiments of the invention will now be described by way of example with, reference to the accompanying drawings in which:

Figure 1 is an axial secticral view of the upper half of the centrifugal pump and gearbox portion of a portable fire puπp.

Figure 2 is an axial sectional view of a centrifugal supercharger and epicyclic gearbox assembly mounted on an engine.

A portable fire pump, part of which is shown in figure 1 comprises a reciprocatory piston-and-cylinder engine 10 of which portions of the crankcase 11 and crankshaft 12 are shown, the output end 13 of the crankshaft 12 being supported in the crankcase 11 by means of a plain bearing 14.

A gearbox casing 15 has external flanges 16 and 17 which are respectively secured by rings of cap screws 18 and 19 to the end face of the crank case 11 and to the casing 21 of a centrifugal pump 20.

A pump shaft 22 carries a puπp rotor 23 forming an impeller is rotably supported in the gearbox casing 15 by a plain bearing 24. The shaft 22 is further supported in an extension 25 of the crankshaft end journal 13 by means of a further plain bearing sleeve 26 which is free-floating and formed with a central ring of oil- holes 26a which register with one or more radial drillings 26b in the puπp shaft

The extension 25 is externally splined to engage the hub 27 on a powder coupling 28. At each end, the hub 27 has a frusto-conical surface 29A, 29B to engage a corresponding centering ring 30A, 30B so as to centre the hub 27 accurately relative to the crankshaft extension 25 when a nut 31 on the end thereof is tightened.

Secured to the hub 27 by a ring of cap screws 32 is the two-part casing 33A, 33B of the powder coupling 28. 3he two casing parts are secured together by tie bolts 34 and define a chamber C containing powder in the form of steel shot and an output element 35 in the form of a corrugated washer bolted to the internally toothed ring gear 37 of a epicyclic gear set 36. The ring gear 37 is supported b pair of ball bearings 38. The chamber C is sealed against loss of the powder by appropriate seals 39 which in turn are protected from oil contamination by further oil seals 40.

The sun gear 41 is splined onto the puπp shaft 22 and secured by a nut 42. A set of planet pinions 43 of the epicyclic gear set 36 is journaled (by free-floating bushes 43a having oil holes 43b) on pins 44 of a planet carrier 45 secured to radial wall 46 of the housing 15.

A rotary seal 47 protects the bearing 24 from the ingress of water (or other liquid being pumped) and is itself protected by an oil seal 48, both seals being mounted in a bore 49 in the casing 15 and cooperating with the punp shaft 22.

In order to provide pressurised lubrication for all of the journal bearings within the casing 15, an axial passage 51 is drilled in the end portion 25 of the crankshaft 12 to c iuiunicate with the normal passages 52 formed therein for supplying pressurised lubricant to the journal bearing 13, 14 as well as to th big end bearings (not shown). The passage 51 αOTπunicates with the passage 53 in the puπp shaft 22 and thus with the drillings 26b. The end of passage 53 oαmiunicates with a radial passage 54 supplying lubricant to the puπp shaft bearing 24. A radial passage 54 also supplies lubricant to a set of radial passages 55 drilled in the wall 46 and plugged at their outer ends at 56.

Lubricant is supplied under pressure from the radial drillings 55 to the pins 44 through side passages 57 which lead into drillings 58 and 59 in the pins 44 comπunicating with the oil holes 43b and thus both the inner and the outer .surfaces of the bearing bushes 43a.

Thus, in operation, oil under pressure from the normal lubrication system of the engine is delivered from the passage 51 into the passage 53 (with the bearing 26 forming a substantially oil tight seal, although, of course, there will be some slight loss of oil from this bearing). Both the inner and the outer surfaces of bearing 26 are thereby pressure-fed with lubricant. Similarly, bearing 24 is pressure fed with lubricant through the passage 54 which also supplies the bearings for the planet pinions 43 with oil under pressure. Further, the ball bearings 38 and the teeth of the gears 37, 41 and 43 will be lubricated by the oil mist created by the oil escaping fran the pressure-fed bearings.

Drainage passages (not shown) in the lower part of the gear case 15 and the crank case 11 return the oil to the normal sump formed in th lower part: of the crank case 11.

The powder coupling 28 protects the epicyclic gear set 36 from torsional vibrations generated wit_hin the engine 10 which might otherwise damage the gear teeth. It can also provide a degree of slip on starting up.

In the supercharger arrangement shown in figure 2, parts corresponding to parts shown in figure 1 are shown by the same reference numeral increased by 100.

The supercharger 120 is of the centrifugal type having a volute casing 121 secured by cap-screws 119 to a back plate 101 which is in turn secured by further cap-screws 102 to a gear box housing 115 mounted on the engine crankcase 111.

An output hub 103 is secured to the end 113 of the crank shaft of the engine by means of a key 104 and a cap nut 105. A planet carrier 145 is secured to the hub 103 by cap-screws 106. A sun gear 141 is journalled at one end in a free-floating bearing 126 in the planet carrier 145 and at its other end in a free-floating bearing 124 in a cover meπtoer 107 secured to the back plate 101 of the supercharger by cap-screws 108. Formed integrally with the sun gear 141 is a rod-like extension 161 carrying at its free end a nut 162 and washer 163 which clamp the supercharger rotor 123 against a rotating seal member 164 and the latter, in turn, against the end face of the right hand journal portion of the sun gear 141.

A stationary sector-shaped seal member 165 is engaged in an annular groove in the rotating seal member 164 and is held in sealing contact with both the rotary seal member 164 and a surface of the cap member 107 by a frusto-σonical spring washer 166.

Planet pinions 143 of larger diameter than the sun gear 141 mesh with the latter and with a internally toothed annulus 137 which is secured to the gear box housing 115 by cap-screws 167. The planet pinions 143 are rotatably mounted by means of free-floating plain bearings 168 on pins 144 fixed in the planet carrier 145, the bearings 168 having oil holes 168a.

Oil under pressure is supplied to the elements described above from the engine lubrication system through a central duct 151 in the crank shaft 112 through a side duct 171 in the crank shaft which leads into a duct 172 in the hub 103 and the planet carrier 145 leading up to drillings 173 in the pins 144 to supply oil to both inner and outer faces of the bearings 168 for the planet pinions 143. The duct 151 is continued by further central ducts 174, 175 and 176 in the crank shaft portion 113, a cap nut 105 and the sun pinion 141 to supply oil under pressure to both faces of the bearings 126 and 124 of the sun gear 141 which also carries the rotor 123.

The seal formed by the rotating seal member 164 and the stationary seal 165 is lubricated under pressure by oil from the bearing 124 through a further duct 177 formed in the cap member 107. Oil escaping from this seal is returned to the interior of the gearbox housing 115 through a passage 178. This oil together with oil from the other bearings described above is returned to the engine suπp through a return duct 179 formed in the gearbox housing 115.

If desired, a disengageable clutch may be included at a convenient point in the drive between the engine crankshaft and the rotor of the supercharger. This clutch may either be under the operator's control or under the operation of an electronic engine management systen for the engine which system also controls other factors such as fuel delivery and ignition t__ming in the case of a spark-ignition engine.

Claims (7)

1. An engine and gearbox assembly σoπprising an internal combustion engine having an output shaft and a pressurised lubrication system ^•i-nr.1-nr.ing a passage in the output shaft, and a speed-changing gearbox an input element of which is drivably connected to the output shaft, wherein a pressurised lubricant supply duct in the output shaft extends axially from the said passage through a substantially pressure-tight bearing into a further passage in an element of the gearbox which is coaxial with the output shaft, the said further passage forming part of a pressurised lubricant supply system for the gearbox fran which lubricant can return to the engine sump.

2. An assembly according to claim 1, wherein the gearbox is a planetary gearbox having a planet carrier carrying pressure- lubricated planet pinions meshings with a sun and/or ring gear.

3. An assembly according to claim 2, wherein the gearbox is an epicyclic gearbox.

4. An assembly according to claim 2 or 3 having lubricant ducts connecting the said further passage for planet pinions of the gearbox.

5. An assembly according to claim 3, wherein the planet carrier is secured to the engine output shaft, the lubricant ducts in the planet carrier are connected to the supply duct and the said further passage is connected to supply lubricant to the sun gear or ring gear bearings.

6. An assembly according to any of the preceding claims wherein at least one of the bearings σoπprises a free-floating sleeve or bush having a lubricant passage through the wall thereof.

7. An assembly according to any of the preceding claims wherein the engine is a reciprocatory piston-and-cylinder engine and the input element of the gearbox is drivably connected to the output shaft through a coupling capable of sufficient slip to absorb torsion oscillations of the output shaft.