Oil pump unit for engine

Information

  • Patent Grant
  • 6732700
  • Patent Number
    6,732,700
  • Date Filed
    Monday, August 13, 2001
    23 years ago
  • Date Issued
    Tuesday, May 11, 2004
    20 years ago
Abstract
An oil pump unit for an engine includes an improved construction. The pump unit includes a housing. A scavenge pump assembly is disposed in series with the feed pump assembly to be driven by the pump shaft. The feed and scavenge pump assemblies each defines end portions spaced apart from each other along the shaft axis. The housing defines a first inlet port and at least one outlet port at one of the end portions of the feed pump assembly, a second inlet port and a second outlet port at one of the end portions of the scavenge pump assembly, and at least a third inlet port at the other end portion of the scavenge pump assembly.
Description




RELATED APPLICATION




This application is based on Japanese Patent Application No. 2000-175655, filed on Jun. 12, 2000, the entire contents of which are hereby incorporated by reference.




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to an oil pump unit for an engine, and more particularly to an improved oil pump unit that varies a volume of its own pumping chamber with rotation.




2. Description of Related Art




Relatively small watercraft such as, for example, personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries one or more riders. A hull of the watercraft typically defines a rider's area above an engine compartment. An internal combustion engine powers a jet propulsion unit that propels the watercraft by discharging water rearwardly. The engine lies within the engine compartment in front of a tunnel which is formed on an underside of the hull. The jet propulsion unit is placed within the tunnel and includes an impeller that is driven by the engine.




Typically, the watercraft employs a lubrication system that lubricates portions of the engine. Some lubrication systems form a closed-loop. Such a lubrication system includes an oil tank containing lubricant oil, an oil pan forming a lower wall of a crankcase of the engine to which the lubricant oil that has lubricated the engine portions returns, a feed pump supplying the lubricant oil within the oil tank to the engine portions, and a scavenge pump returning the lubricant oil from the oil pan to the oil tank. Optionally, a trochoid pump construction is applied to the feed and scavenge pumps. Both of the pumps can be unitarily formed within a single housing. For example, respective pump assemblies can be disposed on a common shaft, which is journaled for rotation within the housing and driven by the engine, in series with each other.




In this arrangement, the housing has at least two inlet openings connected to respective inlet ports of the feed and scavenge pumps, and also at least two outlet openings connected to respective outlet ports of the feed and scavenge pumps. Generally, any side surfaces of the housing are available for forming the inlet and outlet openings. The pump unit occasionally is mounted on the engine body because the engine body normally defines both the engines portions which need lubrications and the oil pan therein.




SUMMARY OF THE INVENTION




One aspect of the present invention include the realization that a problem can arise with this arrangement when the pump housing is mounted directly to the engine body such that the internal passages on the housing are connected to internal oil passages in the engine body. In this arrangement, one of the pump which is disposed farther from the engine body than the other pump, necessarily has internal passages that connect the inlet and outlet ports of the pump to the inlet and outlet openings, respectively. The internal passages can produce flow resistance and the pumping ability of the pump is limited to the extent that is regulated by the flow resistance. A larger pump assembly may be useful under a certain engine speed, for example, less than 4,000 rpm to resolve the problem. However, such a larger pump assembly is no longer useful when the engine operates in a high speed range such as, for example, 4,000-7,000 rpm, because the lubricant oil is urged out from pumping chambers of the pump assembly immediately after being drawn into the chambers.




A need therefore exists for an oil pump unit for an engine that offers better performance over a broader range of engine speeds.




In accordance with one another aspect of the present invention, an oil pump unit for an internal combustion engine comprises a housing. A shaft extends within the housing and is journaled thereon for rotation about a shaft axis. The shaft is driven by the engine. An inner rotor is affixed to the shaft to rotate with the shaft. An outer rotor is disposed around the inner rotor to be rotated by the inner rotor. The inner and outer rotors together define at least one pumping chamber. A volume of the pumping chamber varies with the rotation of the inner and outer rotors. The inner rotor has first and second end portions spaced apart from each other along the shaft axis. The outer rotor has third and fourth end portions spaced apart from each other along the shaft axis. The housing defines a first inlet port and at least one outlet port at a location where the first end portion of the inner rotor and the third end portion of the outer rotor are positioned. The first inlet port and the outlet port selectively communicate with the pumping chamber with the rotation of the inner and outer rotors. The housing further defines at least a second inlet port at a location where the second end portion of the inner rotor and the fourth end portion of the outer rotor are positioned.




In accordance with another aspect of the present invention, an oil pump unit for an internal combustion engine comprises a housing. A shaft extends within the housing and is journaled thereon for rotation about a shaft axis. The shaft is driven by the engine. A first pump assembly is disposed on the shaft to be driven by the shaft. A second pump assembly is disposed on the shaft in series with the first pump assembly to be driven by the shaft. The first and second pump assemblies each defines end portions spaced apart from each other along the shaft axis. The housing defines a first inlet port and at least one outlet port at one of the end portions of the first pump assembly, a second inlet port and a second outlet port at one of the end portions of the second pump assembly, and at least a third inlet port at the other end portion of the second pump assembly.




In accordance with a further aspect of the present invention, a lubrication system for an internal combustion engine comprises a first oil reservoir arranged to contain lubricant oil. A second oil reservoir is arranged to receive the lubricant oil that has lubricated portions of the engine. An oil pump unit is arranged to supply the lubricant oil within the first oil reservoir to the portions of the engine and to return the lubricant oil within the second oil reservoir to the primary oil reservoir. The oil pump unit comprises a housing. A shaft extends within the housing and is journaled thereon for rotation about a shaft axis. The shaft is driven by the engine. A feed pump assembly is disposed on the shaft to be driven by the shaft. A scavenge pump assembly is disposed on the shaft in series with the feed pump assembly to be driven by the shaft. The feed and scavenge pump assemblies each defines end portions spaced apart from each other along the shaft axis. The housing defines a first inlet port and a first outlet port at one of the end portions of the feed pump assembly, a second inlet port and a second outlet port at one of the end portions of the scavenge pump assembly, and at least a third inlet port at the other end portion of the scavenge pump assembly.











BRIEF DESCRIPTION OF THE DRAWINGS




These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings comprise 13 figures.





FIG. 1

is a side elevational view of a personal watercraft including an oil pump unit for an engine of the watercraft that is configured in accordance with a preferred embodiment of the present invention.





FIG. 2

is a top plan view of the watercraft of FIG.


1


.





FIG. 3

is a front, top and starboard side perspective view of the engine shown in FIG.


1


.





FIG. 4

is a front, top, and port side perspective view of the engine shown in FIG.


1


.





FIG. 5

is a side elevational view of a rear portion of the engine. The forward portion of the engine and an oil tank are shown in phantom line. A transmission and a gear housing are partially shown in section.





FIG. 6

is a top plan and partial sectional view of the transmission construction and the oil pump unit shown in FIG.


5


. The transmission, the oil pump unit and a portion of the engine body are shown in section. The oil pump unit in this figure is illustrated schematically.





FIG. 7

is a schematic rear view of a gear train of the transmission.





FIG. 8

is a flow chart a lubrication system incorporating the oil pump unit and arranged in accordance with the preferred embodiment of the present invention.





FIG. 9

is a sectional view of the oil pump unit taken along the line


9





9


of FIG.


10


.





FIG. 10

is a sectional view of the oil pump taken along the line


10





10


of FIG.


9


.





FIG. 11

is a schematic view of a typical trochoid pump construction that is applied to feed and scavenge pump assemblies in the pump unit.





FIG. 12

is a flow chart of a modification of the lubrication system shown in FIG.


8


.





FIG. 13

is a sectional view of a relief valve applied to the feed pump assembly.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION





FIGS. 1-7

illustrate an overall construction of a personal watercraft


30


which employs an oil pump unit


32


(

FIG. 6

) for an engine


34


of the watercraft


30


that is configured in accordance with a preferred embodiment of the present invention. The oil pump unit


32


has particular utility in the context of a marine drive, such as the personal watercraft


30


for instance, and thus is described in the context of a personal watercraft


30


. The oil pump


32


, however, can be used with other types of watercrafts or marine drives (i.e., jet boats, outboard motors, inboard/outboard motors, etc.) and also certain land vehicles, which includes lawnmowers, motorcycles, go carts, all terrain vehicles and the like. Furthermore, the oil pump unit


32


can be used for a stationary engine as will become apparent to those of ordinary skill in the art.




The personal watercraft


30


includes a hull


36


formed with a lower hull section


38


and an upper hull section or deck


40


. Both the hull sections


38


,


40


are made of, for example, a molded fiberglass reinforced resin or a sheet molding compound. The lower hull section


38


and the upper hull section


40


are coupled together to define an internal cavity


42


. An intersection of the hull sections


38


,


40


is defined in part along an outer surface gunnel or bulwark


44


. The hull


36


, and in particular, the internal cavity or “engine compartment”


42


, houses the engine


34


that powers the watercraft


30


.




As shown in

FIG. 2

, the hull


36


defines a center plane CP that extends generally vertically from bow to stern and along a longitudinal axis of the watercraft


30


, when the watercraft


30


is resting in a normal upright position. Along the center plane CP, the upper hull section


36


includes a hatch cover


48


, a steering mast


50


and a seat


52


one after another from fore to aft.




In the illustrated embodiment, a bow portion


54


of the upper hull section


40


slopes upwardly rearwardly and an opening (not shown) is provided through which the rider can access a front portion of the internal cavity


42


. The bow portion


54


preferably is formed with a pair of cover member pieces which are split another along the center plane CP. The hatch cover


48


is hinged to open or detachably affixed to the bow portion


54


to cover the opening.




The steering mast


50


extends generally upwardly toward the top of the bow portion


54


to support a handle bar


56


. The handle bar


56


is provided primarily for a rider to control the steering mast


50


so as to turn the watercraft


30


in a known manner. The handle bar


56


also carries control devices such as, for example, a throttle lever


58


(

FIG. 2

) for operating throttle valves of the engine


34


.




The seat


52


extends fore to aft along the center plane CP at a location behind the steering mast


50


. The seat


52


is configured generally as a saddle shape so that the rider can straddle it. Foot areas


60


(

FIG. 2

) are defined on both sides of the seat


52


and at the top surface of the upper hull section


40


. The foot areas


60


are formed generally flat.




A seat cushion


62


, which has a rigid backing and is supported by a pedestal section


64


of the upper hull section


40


, forms a portion of the seat


52


. The pedestal section


64


forms the other portion of the seat


52


. The seat cushion


62


is detachably affixed to the pedestal section


64


.




An access opening


66


(

FIG. 2

) is defined on the top surface of the pedestal section


64


, under the seat cushion


62


, through which the rider can access a rear portion of the internal cavity


42


, i.e., an engine compartment. In other words, the seat cushion


62


usually closes the access opening


66


. In the illustrated embodiment, the upper hull section


40


also defines a storage box


68


under the seat


52


. It is to be noted that the engine compartment can be the whole internal cavity


42


or it can be divided into one or more areas by one or more bulkheads (not shown).




A fuel tank


72


is placed in the internal cavity


42


under the bow portion


54


of the upper hull section


40


. The fuel tank


72


is coupled with a fuel inlet port positioned atop the upper hull section


40


through a fuel duct. A closure cap


74


(

FIG. 2

) closes the fuel inlet port. The opening disposed under the hatch cover


48


is available for accessing the fuel tank


72


.




A pair of air or ventilation ducts


76


is provided on both sides of the bow portion


54


so that the ambient air can enter the internal cavity


42


through the ducts


76


. Except for the air ducts


76


, the internal cavity


42


is substantially sealed to protect the engine


34


, a fuel supply system including the fuel tank


72


and other systems or components from water. Optionally, the watercraft


30


can include other air ducts (not shown).




The engine


34


preferably is placed within the engine compartment


42


and generally under the seat


52


, although other locations are also possible (e.g., beneath the steering mast


50


or in the bow). The rider can access the engine


34


through the access opening


66


by detaching the seat cushion


62


from the pedestal section


64


.




A jet pump assembly


80


propels the watercraft


30


. The jet pump assembly


80


is mounted in a tunnel


82


formed on the underside of the lower hull section


38


. Optionally, a bulkhead can be disposed between the tunnel


82


and the engine


34


.




The tunnel


82


has a downward facing inlet port


84


opening toward the body of water. A jet pump housing


86


is disposed within a portion of the tunnel


82


and communicates with the inlet port


84


. An impeller is journaled within the jet pump housing


86


.




An impeller shaft


87


extends forwardly from the impeller and is coupled with a crankshaft


88


of the engine


34


by a coupling member


89


to be driven by the crankshaft


88


. More specifically, as shown in

FIGS. 5 and 6

, the coupling member


89


preferably is affixed to one end of an intermediate shaft


90


that has a reduction gear


91


on the other end thereof. The crankshaft


88


also has an output gear


92


that meshes with the reduction gear


91


at a rear end of the crankshaft


88


to rotate the intermediate shaft


90


. Because a diameter of the reduction gear


91


is greater than a diameter of the output gear


92


, the intermediate shaft


90


rotates in a reduced speed that is slower than an engine speed made by the crankshaft


88


.




With reference to

FIG. 1

, the rear end of the jet pump housing


86


defines a discharge nozzle


94


. A deflector or steering nozzle


96


is affixed to the discharge nozzle


94


for pivotal movement about a generally vertical steering axis. A cable connects the deflector


96


with the steering mast


50


so that the rider can steer the deflector


96


.




When the crankshaft


88


of the engine


34


drives the impeller shaft


88


and hence the impeller rotates, water is drawn from the surrounding body of water through the inlet port


84


. The pressure generated in the jet pump housing


86


by the impeller produces a jet of water that is discharged through the discharge nozzle


94


and the deflector


96


. The water jet thus produces thrust to propel the watercraft


30


. The rider can steer the deflector


96


with the handle bar


56


of the steering mast


50


so as to turn the watercraft


30


.




The engine


34


preferably operates on a four-cycle combustion principle and preferably has four cylinders spaced apart from one another along the center plane CP. The engine


34


can have a typical and conventional four-cycle engine construction. That is, the engine


34


includes a cylinder block


98


(

FIG. 4

) defining four cylinder bores in which pistons reciprocate. At least one cylinder head member is affixed to the upper end of the cylinder block


98


to close respective upper ends of the cylinder bores and defines combustion chambers with the cylinder bores and the pistons. Separate cylinder head members for each cylinder bore also can be used.




A crankcase member


99


(

FIGS. 4-6

) also is affixed to the lower end of the cylinder block


98


to close the respective lower ends of the cylinder bores and to define a crankcase chamber with the cylinder block


98


. The crankshaft


88


is journaled for rotation on bearings within the crankcase chamber and is rotatably connected to the pistons through connecting rods. The cylinder block


98


, the cylinder head and the crankcase member


99


preferably are made of aluminum alloy and together define an engine body


100


. The illustrated engine


34


, however, merely exemplifies one type of engine. Other types of engines having other number of cylinders, other cylinder arrangements (V-type and W-type) and operating on other combustion principles (e.g., two-cycle, rotary, diesel) all are applicable.




With referende to

FIGS. 5-7

, the reduction and output gears


91


,


92


preferably are positioned within a gear chamber


101


defined within a gear housing


102


which is affixed at a rear end of the crankcase member


99


. The intermediate shaft


90


extends generally horizontally through an opening


103


of the gear housing


102


toward the impeller shaft


87


. A seal member can provide a water-tight seal at the opening


103


. An external portion of the intermediate shaft


90


is journaled on bearings


104


mounted to the engine body


100


.




Engine mounts


105


(

FIGS. 3 and 4

) extend from both sides of the engine body


100


. The engine mounts


105


preferably include resilient portions made of, for example, a rubber material. The engine body


100


is mounted on the lower hull section


38


(or possibly on the hull liner) by the engine mounts


105


so that vibration of the engine body


100


is inhibited from conducting to the hull section


38


.




The engine


34


comprises an air induction system, a fuel supply system, an ignition system and an exhaust system, although other systems can optionally be provided. The air induction system is arranged to introduce air to the combustion chambers. Throttle valves preferably are provided to regulate the air or measure an amount of the air passing through the induction system.




In the illustrated embodiment, a plenum chamber assembly


108


(

FIGS. 3 and 4

) is provided to collect and filter induction air and to reduce intake noise. The plenum chamber assembly


108


preferably is mounted on the engine body


100


. Throttle bodies journaling the throttle valves for pivotal movement preferably are housed within the plenum chamber assembly


108


.




The fuel supply system is arranged to supply fuel to the combustion chambers within the engine body


100


. A port injected or indirect fuel injection device preferably is employed to spray the fuel into intake ports of the induction system under control of a control device such as, for example, an ECU (Electronic Control Unit) (not shown). Preferably, initiation timing and duration of the injections are controlled by the ECU. A direct fuel injection system that sprays fuel directly into the combustion chambers of course can replace the port injection device. Moreover, other fuel charge forming devices such as, for example, a carburetor assembly can be used instead of the fuel injection system.




The ignition system is arranged to fire air/fuel charges in the combustion chambers at controlled ignition timings. The ECU preferably controls the ignition timings also.




The exhaust system is arranged to guide exhaust gases from the combustion chambers to a location outside of the watercraft


30


. In the illustrated embodiment, the exhaust gases are discharged to the tunnel


82


through a plurality of exhaust manifolds, conduits and/or devices


112


-


124


, described in greater detail below.




A large part of the respective constructions and arrangements of the foregoing systems are well known to those of ordinary skill in the art. A co-pending U.S. patent application filed Jan. 17, 2001, titled ENGINE FOR WATERCRAFT, which serial number is Ser. No. 09/765,052, and also a co-pending application filed Jul. 31, 2001, titled FOUR-CYCLE ENGINE, disclose exemplary constructions and arrangements, the entire contents of which are hereby expressly incorporated by reference.




As shown in

FIG. 3

, first and second exhaust manifolds


112


,


114


depend from the cylinder head member at a starboard side surface thereof. The exhaust manifolds


112


,


114


define outer exhaust passages that are coupled with inner exhaust passages defined within the cylinder head member to collect exhaust gases from the respective inner exhaust passages. More specifically, the first exhaust manifold


112


has a pair of end portions spaced apart from each other with a length that is equal to a distance between the forward-most inner exhaust passage and the rear-most inner exhaust passage. The end portions are connected with the forward-most and rear-most exhaust passages. The second exhaust manifold


114


also has a pair of end portions spaced apart from each other with a length that is equal to a distance between the other two or in-between exhaust passages. The end portions of the second exhaust manifold


114


are connected with the in-between exhaust passages. The exhaust manifolds


112


,


114


extend slightly downwardly. Respective downstream ends of the first and second exhaust manifolds exist closely with one another and are coupled with an upstream end of a first unitary exhaust conduit


116


.




The first unitary conduit


116


extends further downwardly and then upwardly as it extends forwardly and in a downstream direction of the exhaust system. A downstream end of the first unitary conduit


116


is coupled with an upstream end of a second unitary exhaust conduit


118


. The second unitary conduit


118


extends further upwardly and then transversely to end in front of the engine body


100


. As shown in

FIG. 4

, the second unitary conduit


118


is coupled with an exhaust pipe


120


on the front side of the engine body


100


. The coupled portions thereof preferably are supported by a front surface of the engine body


100


. The exhaust pipe


120


extends rearwardly along a side surface of the engine body


100


on the port side and then is connected to an exhaust silencer or water-lock


122


at a forward surface of the exhaust silencer


122


.




With reference to

FIG. 2

, the exhaust silencer


122


preferably is placed at a location generally behind the engine body


100


but in a half space on the port side and is secured to the lower hull section


38


(or possibly to a hull liner). A discharge pipe


124


extends from a top surface of the exhaust silencer


122


and transversely across the center plane CP to the other half space on the starboard side. The discharge pipe


124


then extends rearwardly and opens at the tunnel


82


and thus to the exterior of the watercraft


30


in a submerged position. The exhaust silencer


122


has one or more expansion chambers to reduce exhaust noise and also to inhibit water in the discharge pipe


124


from entering the exhaust pipe


120


when the watercraft


30


capsizes because of its construction and arrangement as is well known.




As shown in

FIG. 3

, the exhaust system preferably is provided with a secondary air delivery device


126


that can purify the exhaust gases by oxidation reaction with oxygen that is supplied to the exhaust system through the device


126


.




The watercraft


30


preferably employs a cooling system for the engine


34


and the exhaust system. Preferably, the cooling system is an open-loop type and includes a water pump and a plurality of water jackets and/or conduits. In the illustrated embodiment, the jet pump assembly


80


is used as the water pump with a portion of the water pressurized by the impeller being drawn off for the cooling system, as known in the art.




The engine body


100


and the respective exhaust manifolds and conduits


112


-


120


preferably define the water jackets. Both portions of the water to the water jackets of the engine body


100


and to the water jackets of the exhaust system can flow through either common channels or separate channels formed within one or more exhaust manifolds and conduits


112


-


120


or external water pipes. The illustrated exhaust manifolds and conduits


112


-


120


preferably are formed as dual passage structures in general.




With primary reference to

FIGS. 6-11

and continued reference to

FIGS. 3-5

, a preferred construction and arrangement of a lubrication system


130


that includes the oil pump unit


32


is described below.





FIG. 8

illustrates a block diagram schematically showing the lubrication system


130


. The lubrication system


130


is employed for delivering lubricant oil to engine portions


132


that benefit from lubrication and for collecting the oil for recirculation. The engine portions


132


includes, for example, coupling portions of the crankshaft


88


, pistons, connecting rods and respective bearings as is well known to those of ordinary skill in the art. The illustrated lubrication system


130


is a closed-loop, dry-sump type, although other types can of course be applied.




The lubrication system


130


preferably comprises an oil tank or primary oil reservoir


134


and an oil cap or temporary oil reservoir


138


other than the oil pump unit


32


. As shown in

FIGS. 3-5

, the oil tank


134


preferably is configured as a rectangular parallelepiped reservoir for storing lubricant oil. The oil tank


134


is disposed, for example, on a rear side of the engine body


100


and is mounted on the engine body


100


or directly affixed to the lower hull section


38


. The oil cap


138


is formed at a bottom of the crankcase chamber that is defined by the crankcase member


99


. That is, the oil cap


138


is located under the engine portions


132


in the engine body


100


.




As schematically shown in

FIG. 6

, the oil pump unit


32


is mounted on the gear housing


102


adjacent to the bearings


104


on which the intermediate shaft


90


of the coupling member


89


is journaled. The oil pump unit


32


comprises a feed pump assembly


142


and a scavenge pump assembly


144


.




With reference to

FIG. 8

, the oil pump unit


32


preferably has two inlet openings


148


,


150


and two outlet openings


152


,


154


. The inlet opening


148


is connected with the oil tank


134


through a supply passage


158


, while the inlet opening


150


is connected with the oil cap


138


through an external scavenge passage


160


. The outlet opening


152


in turn is connected with the engine portions


132


through one or more delivery passages


162


, while the outlet opening


154


is connected with the oil tank


134


through an external return passage


164


.




Internally, the feed pump assembly


142


preferably has an inlet port


168


connected with the inlet opening


148


and an outlet port


170


connected with the outlet opening


152


. The scavenge pump assembly


144


in turn advantageously has a pair of inlet ports


174


,


176


and a pair of outlet ports


178


,


180


. The inlet port


174


is connected with the inlet opening


150


through an internal scavenge passage


184


, while the inlet port


176


also is connected with the inlet opening


150


through a branch passage


186


and then through the scavenge passage


184


. The outlet port


178


in turn is connected with the outlet opening


154


through an internal return passage


188


, while the outlet port


180


also is connected with the outlet opening


154


through a branch passage


190


and then through the return passage


188


.




With primary reference to

FIGS. 6 and 8

, the oil pump unit


32


preferably comprises a housing


194


, a pump shaft


196


, inner and outer feed pump rotors


198


,


200


, and inner and outer scavenge pump rotors


202


,


204


. The housing


194


preferably comprises first, second and third housing members


206


,


208


,


210


which are coupled together by through bolts.

FIG. 10

shows bolt holes


212


for the bolts. Preferably, the first or front housing member


206


has flanges (not shown) to be affixed to the gear housing


102


by bolts. The second or middle housing member


208


forms a feed pump space


214


and a scavenge pump space


216


. The inner and outer feed pump rotors


198


,


200


have respective end portions axially spaced apart from each other and are disposed within the feed pump space


214


, while the inner and outer scavenge pump rotors


202


,


204


also have end portions axially spaced apart from each other and are disposed within the scavenge pump space


216


. The pump shaft


196


extends generally horizontally within the housing


194


in parallel to the intermediate shaft


90


and is journaled on the front and rear housing members


206


,


210


. The pump shaft


196


preferably has a uniform diameter throughout.




The pump shaft


196


is driven by the crankshaft


88


. In the illustrated embodiment, a pump gear


220


meshes with the output gear


92


of the crankshaft


88


on an opposite side to the reduction gear


91


, and a pump gear shaft


222


of the pump gear


220


is coupled with the pump shaft


196


. An axis


223


of the pump gear shaft


222


is coincident with an axis of the pump shaft


196


.




The gear housing


102


has a cylindrical bearing portion


224


in which the pump gear shaft


222


extends to be journaled thereon. The pump gear shaft


222


has a coupling recess


226


at a rear end thereof, while the pump shaft


196


has a coupling projection


228


that fits in the coupling recess


226


. The pump shaft


196


thus rotates together with the pump gear shaft


222


which is driven by the crankshaft


88


through the meshed output gear


92


and the pump gear


220


.




As shown in

FIGS. 6 and 7

, the output gear


92


, the reduction gear


91


and the pump gear


220


together form a gear train


230


. Because a diameter of the pump gear


220


is greater than the diameter of the output gear


92


and is generally equal to the diameter of the reduction gear


91


, the pump gear shaft


222


and the pump shaft


196


rotates slower than the crankshaft


88


and can be approximately the same speed as the intermediate shaft


90


.




With reference to

FIGS. 9 and 10

, the pump shaft


196


preferably is journaled on bearing portions


234


,


236


,


238


of the front, middle, and rear housing members


206


,


208


,


210


, respectively. The illustrated feed and scavenge pump spaces


214


,


216


are formed in series with each other on the pump shaft


196


. In other words, the scavenge pump space


216


is spaced apart from the feed pump space


214


along the axis


223


of the pump shaft


196


. Preferably, the feed pump space


214


is disposed closer to the gear housing


102


, i.e., the engine body


100


. A seal member


240


is provided around the pump shaft


196


between the feed and scavenge pump spaces


214


,


216


to liquid-tightly separate both the spaces


214


,


216


.




The inner and outer rotors


198


,


200


together define the feed pump assembly


142


with the pump shaft


196


and the middle housing member


208


, while inner and outer rotors


202


,


204


together define the scavenge pump assembly


144


also with the pump shaft


196


and the middle housing member


208


. In the illustrated embodiment, both the feed and scavenge pump assemblies


142


,


144


have a typical trochoid pump construction.




As schematically shown in

FIG. 11

, the respective inner rotors


198


,


202


preferably have four teeth and affixed to the pump shaft


196


to rotate together with the pump shaft


196


. As shown in

FIG. 9

, the pump shaft


196


defines key ways


248


,


250


positioned at the feed and scavenge pump spaces


214


,


216


. Keys


252


,


254


coupled with the pump shaft


196


engage with the respective key ways


248


,


250


to rotate the inner rotors


198


,


202


with the pump shaft


196


. The outer rotors


200


,


204


are disposed around the inner rotors


198


,


202


. The respective outer rotors


200


,


204


define five recesses in which the teeth of the inner rotors


198


,


202


are engageable.

FIG. 10

shows an outer surface of the outer rotors


200


,


204


with a phantom line


258


. As shown in

FIGS. 10 and 11

, the pump shaft


196


is slightly offset from a center axis of the outer rotors


200


,


204


.




Because of the configurations and arrangements of the inner and outer rotors


198


,


200


,


202


,


204


, the outer rotors


200


,


204


are rotated by the inner rotors


198


,


202


with a certain lost motion relative to the inner rotors


198


,


202


. As a result, pumping chambers


260


,


262


, which volumes vary with the rotations of the pump shaft


196


, are formed between the inner and outer rotors


198


,


200


and also between the inner and outer rotors


202


,


204


.




With reference to

FIG. 9

, the inlet and outlet ports


168


,


170


of the feed pump assembly


142


preferably are formed in the front housing member


206


on one side, i.e., on a front side, of the feed pump assembly


142


. In other words, the inlet and outlet ports


168


,


170


are defined next to one end, i.e., front end, of the inner and outer rotors


198


,


200


. Similarly but on both sides of the scavenge pump assembly


144


, the inlet and outlet ports


174


,


176


,


178


,


180


are formed. That is, the inlet and outlet ports


174


,


178


of the scavenge pump assembly


144


preferably are formed in the rear housing member


210


on one side, i.e., on a rear side, of the scavenge pump assembly


142


, while the inlet and outlet ports


176


,


180


of the scavenge pump assembly


144


are formed in the middle housing member


208


on the other side, i.e., preferably on a front side, of the scavenge pump assembly


142


. In other words, the inlet and outlet ports


174


,


178


are defined next to one end, i.e., rear end, of the inner and outer rotors


202


,


204


, while the inlet and outlet ports


176


,


180


are defined next to the other end, i.e., front end, of the inner and outer rotors


202


,


204


.




The inlet and outlet ports


168


,


170


of the feed pump assembly


142


are configured as generally the same arcs and do not communicate with each other. When one of the pumping chambers


260


of the feed pump assembly


142


communicates with the inlet port


168


and moves for a while, the volume of the pumping chamber


260


increases and hence lubricant oil is drawn into the pumping chamber


260


through the inlet port


168


. Afterwards, when the pumping chamber


260


communicates with the outlet port


170


and moves for a while, the volume of the pumping chamber


260


decreases and hence lubricant oil is pushed out from the pumping chamber


260


through the outlet port


170


. Same situations occur with other pumping chambers


260


continuously with the rotation of the pump shaft


196


.




In contrast, the respective inlet and outlet ports


174


,


176


,


178


,


180


are configured as generally the same arcs. The inlet and outlet ports


174


,


178


do not communicate with each other. Similarly, the inlet and outlet ports


176


,


180


do not communicate with each other. When one of the pumping chambers


262


of the scavenge pump assembly


144


communicates with both the inlet ports


176


,


174


and moves for a while, the volume of the pumping chamber


262


increases and hence lubricant oil is drawn into the pumping chamber


262


through the inlet ports


174


,


176


. Afterwards, when the pumping chamber


262


communicates with both the outlet ports


178


,


180


and moves for a while, the volume of the pumping chamber


262


decreases and hence lubricant oil is pushed out from the pumping chamber


262


through the outlet ports


178


,


180


. The same situation occurs with the other pumping chambers


262


continuously with the rotation of the pump shaft


196


.




With reference to

FIG. 9

, the inlet port


168


of the feed pump assembly


142


is connected with the inlet opening


148


without any substantial interconnecting passage. The outlet port


170


of the feed pump assembly


142


also is connected with the outlet opening


152


without any substantial interconnecting passage. The internal scavenge passage


184


that connects the inlet port


174


with the inlet opening


150


is formed within the front, middle, and rear housing members


206


,


208


,


210


to extend generally in parallel to the axis of the pump shaft


196


out of the feed and scavenge pump assemblies


142


,


144


. The branch passage


186


is defined within the middle housing member


176


to branch off from the internal scavenge passage


184


.




The illustrated branch passage


186


can be formed by drilling from outside of the housing member


208


so that an axis of the branch passage


186


extends generally normal to an axis of the internal scavenge passage


184


. A closure plug


270


closes an opening


272


made in the drilling process. The inlet opening


150


thus is positioned oppositely from the pump shaft


196


relative to the inlet opening


148


on the same side of the housing


194


where the housing


194


is mounted on the gear housing


102


. This is advantageous because the external conduits or pipes


158


,


162


can be as short as possible.




The internal return passage


188


that connects the outlet port


178


with the outlet opening


154


in turn is formed within the front, middle, and rear housing members


206


,


208


,


210


to extend generally parallel to the axis of the pump shaft


196


out of the feed and scavenge pump assemblies


142


,


144


. The branch passage


190


is defined within the middle housing member


176


to merge with the internal return passage


188


. The illustrated branch passage


190


also can be formed by drilling from outside of the housing member


208


so that an axis of the branch passage


190


extends generally normal to an axis of the internal return passage


188


. A closure plug


274


closes an opening


276


made in the drilling process.




As shown in

FIG. 10

, the respective branch passages


186


,


190


preferably cross one another with an angle such as, for example, approximately 60 degrees. The outlet opening


154


thus is positioned oppositely from the pump shaft


196


relative to the outlet opening


170


on the same side of the housing


194


where the housing


194


is mounted on the gear housing


102


as well as the inlet openings


148


,


150


. That is, all of the inlet and out let openings


148


,


150


,


152


,


154


are formed between the gear housing


102


and the front housing member


206


, i.e., the pump housing


194


. This is also advantageous because the external conduits or pipes


160


,


164


can be as short as possible.




Either the feed or scavenge pump assembly


142


,


144


can be positioned adjacent to the gear housing


102


. In the illustrated embodiment, the feed pump assembly


142


is advantageously located next to the gear housing


102


because, in general, the feed pump assembly


142


is more important than the scavenge pump assembly


144


. That is, a closer location does not need substantial passages that increase flow resistance than the other location and hence the feed pump assembly


142


in this location can be more powerful than the scavenge pump assembly


144


.




As described above, in the illustrated embodiment, the scavenge pump assembly


144


has two pairs of inlet and outlet ports


174


,


176


,


178


,


180


on both sides thereof. Because of this arrangement, the lubricant oil can immediately enter the pumping chambers


262


and expand with less delay during filling the entire volume of the respective chambers


262


. Accordingly, a relatively large volume of scavenge pump assembly


144


can be applicable. As shown in

FIG. 9

, the illustrated scavenge pump assembly


144


thus is configured larger than the feed pump assembly


142


. That is, a length L


1


between both the ends of the inner and outer rotors


202


,


204


of the scavenge pump assembly


144


is longer than a length L


2


between both the ends of the inner and outer rotors


198


,


200


. Of course, the scavenge and feed pump spaces


216


,


214


have generally the same lengths L


1


, L


2


, respectively, to house them therein. Preferably, the length L


1


is one and a half times as long as the length L


2


. Because of this dimensional relationship, the volume of the pumping chambers


262


of the scavenge pump assembly


144


is greater than the volume of the pumping chambers


260


of the feed pump assembly


142


. Incidentally, the bearing portion


236


of the in-between housing member


208


preferably has an axial length L


3


that is shorter than the length L


1


and longer than the length L


2


.




As the oil pump unit


32


operates along with the operation of the engine


34


, the lubricant oil in the oil tank


134


flows through the supply passage


158


and is drawn into the pumping chambers


260


of the feed pump assembly


142


through the inlet opening


148


of the oil pump unit


32


and the inlet port


168


of the feed pump assembly


142


. The feed pump assembly


142


feeds the lubricant oil from the pumping chambers


260


to the engine portions


132


through the outlet port


170


of the feed pump assembly


142


and then the outlet opening


152


of the oil pump unit


32


and further through one or more delivery passages


162


. The lubricant oil lubricates the engine portions


132


and falls down to the oil cap


138


by its own weight. The lubricant oil in the oil cap


138


then flows through the external scavenge passage


160


and is drawn to the oil pump unit


32


at another inlet opening


150


. The lubricant oil then proceeds through the internal scavenge passage


184


to the inlet port


174


of the scavenge pump assembly


144


as indicated by an arrow A of FIG.


9


and then is drawn into the pumping chambers


262


.




Simultaneously, a portion of the oil is branched off to the inlet port


176


through the branch passage


186


as indicated by an arrow B of FIG.


9


and is drawn into the pumping chambers


262


. The scavenge pump assembly


144


pressurizes the lubricant so as to flow toward the oil tank


134


from the outlet ports


178


,


180


. The oil in the pumping chambers


262


flows out through both the outlet ports


178


,


180


as indicated by arrows C and D of FIG.


9


. The lubricant oil from the outlet port


178


proceeds through the internal return passage


188


and the oil from the outlet port


180


goes through the branch passage


190


and then merges with the oil proceeding through the internal return passage


188


. The lubricant oil that has passed through the internal return passage


188


flows out to the external return passage


164


from the outlet opening


154


. This circulation of the lubricant oil continues as the engine


34


operates.




During the operation of the oil pump unit


32


, the rotational speed of the pump shaft


196


varies in response to changes in engine speed, i.e., the rotational speed of the crankshaft


88


. The inner and outer rotors


202


,


204


of the scavenge pump assembly


144


, which are positioned farther from the inlet and outlet openings


150


,


154


in this embodiment, also rotate with the rotation of the pump shaft


196


. Because it has a larger volume, the scavenge pump assembly


144


provides a desirable flow rate of the return oil to the oil tank


134


. Since the pairs of inlet and outlet ports


174


,


176


,


178


,


180


on both the sides of the scavenge pump assembly


144


can have the oil immediately expand to fill the pumping chambers


262


even under a high speed rotational condition of the pump shaft


196


, the pump unit


32


provides enhanced oil flow over a larger range of pump shaft


196


speeds. It should be noted that the respective locations of the feed and scavenge pump assemblies within the pump unit are interchangeable with each other.




The outlet ports


178


,


180


of the pump assembly, which is the scavenge pump assembly


144


in the embodiment, are not necessarily a pair on both the sides.

FIG. 12

illustrates another embodiment of the oil pump unit


32


. The members and components, which have already been described, are assigned with the same reference numerals and will not be described repeatedly.




In this embodiment, the scavenge pump assembly


144


has only one outlet port


178


, although both the inlet ports


174


,


176


still are provided. This arrangement advantageously expedites the filling of the pumping chambers


262


with lubricant because the lubricant flow out from the chambers


262


is more restricted than the lubricant flow into the chambers


262


. It should be noted again that the respective locations of the feed and scavenge pump assemblies within the pump unit are interchangeable with each other in this embodiment. Also, the outlet port


178


can be omitted instead of the outlet port


180


. In this alternative, the branch passage


190


of course is a portion of the internal return passage


188


.




With reference to

FIG. 13

, the oil pump units


32


illustrated in

FIGS. 8 and 12

, can have a pressure relief construction


280


disposed on a projected portion


282


of the gear housing


102


where the outlet opening


152


of the feed pump assembly


142


is formed. The outlet opening


152


in part is connected with the gear chamber


101


through an aperture


284


defined at the projected portion


282


. The aperture


284


comprises a small diameter portion


285


and a large diameter portion


286


that is positioned closer to the gear chamber


101


than the small diameter portion. In other words, the small diameter portion


285


communicates with the outlet opening


152


, while the large diameter portion


286


communicates with the gear chamber


101


. A relief valve


287


is slideably supported in the small diameter portion


285


. The relief valve


287


defines four through-holes


288


that can open to the large diameter portion


286


when the relief valve


287


moves toward the large diameter portion


286


, i.e., to an open position. A coil spring


290


is disposed around a tip portion of the relief valve


287


within the large diameter portion


286


of the aperture


284


. An end of the spring


290


abuts on a flange portion


292


of the relief valve


287


. Another end of the spring


290


abuts on a retainer assembly


294


that is affixed to the projected portion


282


by a bolt


296


. The spring


290


thus normally urges the relief valve


287


toward the outlet opening


152


to close the through-holes


288


, i.e., to a closed position. The retainer assembly


294


defines a space through which the large diameter portion


286


communicates with the gear chamber


101


.




In the event such that the pressure within the feed pump assembly


142


abnormally increases, the relief valve


287


moves to the open position from the closed position against the bias force of the spring


290


to relieve the pressure toward the gear chamber


101


. As such, a certain amount of the lubricant oil within the feed pump assembly


142


flows into the gear chamber


101


. Afterwards, the spring


290


again biases the relief valve


287


to set it back to the closed position. The gear chamber


101


contains some of the lubricant oil to lubricate the gear train


230


. The lubricant oil entering the chamber


101


thus merges with this lubricant oil and then moves to the oil cap


138


anyway.




It should be noted that the scavenge pump assembly instead can have the relief valve at its outlet opening, or both the feed and scavenge pump assemblies can have the relief valve.




Of course, the foregoing description is that of a preferred construction having certain features, aspects and advantages in accordance with the present invention. Various changes and modifications may be made to the above-described arrangements without departing from the spirit and scope of the invention, as defined by the appended claims.



Claims
  • 1. An oil pump unit for an internal combustion engine comprising a housing, a shaft extending within the housing and journaled thereon for rotation about a shaft axis, the shaft being driven by the engine, a first pump assembly disposed on the shaft to be driven by the shaft, and a second pump assembly disposed on the shaft in series with the first pump assembly to be driven by the shaft, the first and second pump assemblies each defining end portions spaced apart from each other along the shaft axis, the housing defining a first inlet port and at least one outlet port at one of the end portions of the first pump assembly, a second inlet port and a second outlet port at one of the end portions of the second pump assembly, and at least a third inlet port at the other end portion of the second pump assembly.
  • 2. The oil pump unit as set forth in claim 1, wherein the shaft is coupled with an output shaft of the engine at a first location on one side of the housing, and the first pump assembly is disposed next to the first location.
  • 3. The oil pump unit as set forth in claim 1, wherein the housing further defines an inlet passage coupling the second and third inlet ports with each other, and a portion of the inlet passage communicating with the second inlet port is positioned between the first and second pump assemblies.
  • 4. The oil pump unit as set forth in claim 3, wherein the housing still further defines an inlet opening communicating with the inlet passage.
  • 5. The oil pump unit as set forth in claim 4, wherein the inlet opening is formed at a side surface of the housing, and the side surface is positioned closer to the first pump assembly than the second pump assembly.
  • 6. The oil pump unit as set forth in claim 1, wherein the second pump assembly comprises an inner rotor affixed to the shaft to rotate with the shaft and an outer rotor disposed around the inner rotor to be rotated by the inner rotor, the inner and outer rotors together defining at least one pumping chamber, a volume of the pumping chamber varying with rotation of the inner and outer rotors, the second inlet and outlet ports selectively communicating with the pumping chamber with the rotation of the inner and outer rotors.
  • 7. The oil pump unit as set forth in claim 1, wherein a length between the end portions of the second pump assembly is longer than a length between the end portions of the first pump assembly.
  • 8. The oil pump unit as set forth in claim 1, wherein the second pump assembly defines a scavenge pump assembly arranged to collect lubricant oil that has circulated within the engine.
  • 9. The oil pump unit as set forth in claim 8, wherein the first pump assembly defines a feed pump arranged to feed the lubricant oil to the engine.
  • 10. The oil pump unit as set forth in claim 1, wherein the housing defines a third outlet port at the other end portion of the second pump assembly.
  • 11. The oil pump unit as set forth in claim 10, wherein the third inlet and outlet ports selectively communicate with the pumping chamber during rotation of the inner and outer rotors.
  • 12. The oil pump unit as set forth in claim 10, wherein the housing defines an outlet passage coupling the second and third outlet ports with each other, and a portion of the outlet passage communicating with the first outlet port is positioned between the first and second pump assemblies.
  • 13. The oil pump unit as set forth in claim 12, wherein the housing defines an outlet opening communicating with the outlet passage.
  • 14. The oil pump unit as set forth in claim 13, wherein the outlet opening is formed at a side surface of the housing, and the side surface is positioned closer to the first pump assembly than the second pump assembly.
  • 15. The oil pump unit as set forth in claim 1, wherein the engine operates on a four-cycle combustion principle.
  • 16. The oil pump unit as set forth in claim 1, wherein the engine powers a marine propulsion device.
  • 17. A lubrication system for an internal combustion engine comprising a first oil reservoir arranged to contain lubricant oil, a second oil reservoir arranged to receive the lubricant oil that has lubricated portions of the engine, and an oil pump unit arranged to supply the lubricant oil within the first oil reservoir to the portions of the engine and to return the lubricant oil within the second oil reservoir to the first oil reservoir, the oil pump unit comprising a housing, a shaft extending within the housing and journaled thereon for rotation about a shaft axis, the shaft being driven by the engine, a feed pump assembly disposed on the shaft to be driven by the shaft, and a scavenge pump assembly disposed on the shaft in series with the feed pump assembly to be driven by the shaft, the feed and scavenge pump assemblies each defining end portions spaced apart from each other along the shaft axis, the housing defining a first inlet port and a first outlet port at one of the end portions of the feed pump assembly, a second inlet port and a second outlet port at one of the end portions of the scavenge pump assembly, and at least a third inlet port at the other end portion of the scavenge pump assembly.
  • 18. The lubrication system as set forth in claim 17, wherein the first inlet port and the second outlet port are connected to the first oil reservoir, the first outlet port is connected to the portions of the engine, and the second and third inlet ports are connected to the second oil reservoir.
  • 19. The lubrication system as set forth in claim 18, wherein the first outlet port includes a relief valve arranged to allow the lubricant oil in the feed pump assembly to move toward the second oil reservoir when a pressure in the feed pump assembly is greater than a preset pressure.
  • 20. The lubrication system as set forth in claim 17, wherein the shaft is coupled with an output shaft of the engine at a location on one side of the housing, the feed pump assembly is disposed next to the location to extend between the location and the scavenge pump assembly.
  • 21. The lubrication system as set forth in claim 20, wherein the housing an inlet passage coupling the first and second inlet ports with each other, and a portion of the inlet passage communicating with the first inlet port is positioned between the feed and scavenge pump assemblies.
  • 22. The lubrication system as set forth in claim 17, wherein the scavenge pump assembly comprises an inner rotor affixed to the shaft to rotate with the shaft, an outer rotor disposed around the inner rotor to be rotated by the inner rotor, the inner and outer rotors together define at least one pumping chamber, a volume of the pumping chamber varying with rotation of the inner and outer rotors, the second inlet and outlet ports selectively communicating with the pumping chamber with the rotation of the inner and outer rotors.
  • 23. The lubrication system as set forth in claim 17, wherein the housing defines a third outlet port at the other end portion of the scavenge pump assembly.
  • 24. The lubrication system as set forth in claim 23, wherein the third inlet and outlet ports selectively communicate with the pumping chamber during the rotation of the inner and outer rotors.
  • 25. The lubrication system as set forth in claim 17, wherein the first oil reservoir is a primary reservoir of the lubrication system and the second reservoir is a temporary reservoir in the lubrication system.
Priority Claims (1)
Number Date Country Kind
2000-175655 Jun 2000 JP
US Referenced Citations (7)
Number Name Date Kind
5558549 Nakase et al. Sep 1996 A
5839930 Nanami et al. Nov 1998 A
5951343 Nanami et al. Sep 1999 A
6015320 Nanami Jan 2000 A
6247904 Miyazaki et al. Jun 2001 B1
6314934 Ito et al. Nov 2001 B1
6478114 Ito et al. Nov 2002 B2