Ground wire connecting structure

A ground wire connecting structure has a joint unit that is mounted to an oil tank. The joint unit has a base body to which bus bars are attached. Connector sections accommodating ground terminals are connected to the bus bars. The joint unit is coupled to a ground surface that is defined by the oil tank. The base body and the ground surface are made of a metal, such as an aluminum alloy. The base body has a contact portion for surface contact with the ground surface. Connector sections, to which external ground wires are fixed, are connected to the external ground wires and the ground terminals. As such, the external ground wires and the ground surface are electrically coupled with each other. The contact portion between the base body and the ground surface is sealed with an O-ring.

PRIORITY INFORMATION

The present application is based on and claims priority under 35 U.S.C. § 119(a-d) to Japanese Patent Application No. 2004-274445, filed on Sep. 22, 2004, the entire contents of which is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to ground wire connecting structures and, more particularly, to ground wire connecting structures that are mounted to an oil tank.

2. Description of the Related Art

Vehicles having electrical equipment often include ground wire connecting structures. For example, small watercraft automobiles, and boats often include in-vehicle units (e.g., in-vehicle units that include ground wire connecting structures). Japanese Patent Publication No. Hei 2002-301998 discloses an in-vehicle unit for use in automobiles. The in-vehicle unit has an attachment portion made of a conductive material. The in-vehicle unit is attached to a body panel of the vehicle via the attachment portion. A wire harness of an external circuit is connected to the in-vehicle unit. The attachment portion of the in-vehicle unit has a through hole and a projection. The body panel has a threaded hole and a recess that engages the projection of the attachment portion. When the projection engages the recess, a bolt is inserted into the through hole such that the attachment portion is coupled to the body panel. In this manner, the in-vehicle unit is attached to the body panel of the vehicle.

An internal circuit of the in-vehicle unit often has a ground circuit electrically coupled with the attachment portion. The wire harness is typically connected to the in-vehicle unit and includes a ground wire. The ground wire is connected to the body panel via the attachment portion thereby connecting the ground wire to the ground circuit. Thus, the body panel does not need a separate ground wire connecting portion.

Unfortunately these in-vehicle wire connecting structures have a relatively small attachment portion that is fixed to the body panel. A single bolt electrically couples the ground wire with the body panel. Such connections provide poor contact and the in-vehicle unit may not be securely fixed to the body panel.

SUMMARY OF THE INVENTION

An aspect of the present invention includes a ground wire connecting structure for use in a vehicle. The ground wire connecting structure can be securely mounted to a component of the vehicle.

In accordance with one aspect, a ground wire connecting structure for grounding a circuit to a watercraft component is provided. The ground wire connecting structure comprises a joint unit that has a joint unit body and a conductive member mounted thereto. At least one joint unit side connector section has a substantially tubular body that is attached to the joint unit body. The at least one joint unit side connector section is configured to accommodate a ground terminal connected to the conductive member. The joint unit is attached to a ground surface defined by a watercraft component. The ground surface is comprised of a conductive material such that the ground surface and the conductive member are electrically coupled together. An external connector section is coupled to an external ground wire and the at least one joint unit side connector section. The ground wire and the ground terminal are coupled together so that the external ground wire and the ground surface are in electrical communication. The joint unit body is comprised of a conductive material that is in electrically communication with the conductive member. The joint unit body has a contact portion in surface contact with the ground surface. The joint unit body is detachably attached to the ground surface via at least one fastening assembly.

In yet another aspect, a watercraft comprises a first electrical device and a ground wire connecting structure. The ground wire connecting structure comprises a joint unit having a joint unit body and a first joint unit side connector section attached to the joint unit body. The first electrical device is connected to the first joint unit side connector section of the ground wire connecting structure by at least one ground wire. The joint unit is attached to a ground surface defined by a watercraft component. The ground surface and a contact surface of the joint unit contact each other and are made of a conductive material such that the ground surface and a first conductive member mounted to the joint unit body are electrically coupled together. A fastening assembly couples the joint unit body to the ground surface.

In another aspect, the ground wire connecting structure has a joint unit body to which a constructive member is attached. The joint unit body can function as an attachment portion. Also, the joint unit body has a contact portion for surface contact with a ground surface. Thus, the area of the contact portion can be determined by choosing the size of the joint unit body. By enlarging the size of the contact portion, the joint unit body can contact the ground surface. The joint unit body can be securely fixed to the ground surface by one or more fasteners. Further, because the joint unit body forms a base body of the joint unit, the ground wire connecting structure can be made smaller as the joint unit body is reduced in size.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference toFIGS. 1 and 2, an overall configuration of a personal watercraft10and its engine15and a ground wire connecting structure is described below. The described ground wire connecting structure has particular utility with personal watercraft, and thus, it is described in the context of personal watercraft. However, the ground wire connecting structure can also be applied to other types of vehicles, such as small jet boats and other vehicles that feature marine drives, automobiles, motorcycles, scooters, and the like, as well as industrial stationary engines, generators, and other engines, for example. The terms “upper,” “lower,” “top,” “bottom,” “left,” “right,” “fore,” “aft,” and the like may be used to describe the watercraft10. These terms are used in reference to the illustrated embodiment and are from the perspective of a rider straddling a seat13.

The watercraft10has a body11that includes an upper hull section11aand a lower hull section11b.The upper and lower hull sections11a,11bcooperate to define an internal cavity that can form an engine compartment. The engine compartment can be defined by a forward and rearward bulkhead; however, other configurations are also possible. The engine compartment is preferably located under the seat13, but other locations are also possible (e.g. beneath the control mast or the bow).

The watercraft10also includes handlebars12in front of the seat13and on top of the upper hull section11a.The seat13is preferably positioned centrally along the upper side of the upper hull section11a.Additionally, foot mounting steps can be formed at the sides of the body11. Preferably one foot mounting step is on the left side and another foot mounting step is on the right side of the seat13. The seat13has a saddle shape, so that a rider can sit on the seat13in a straddle fashion and often is referred to as a straddle-type seat; however, other types of seats can also be employed.

With continued reference toFIG. 1, a fuel tank14for storing fuel is disposed in front of the engine15. Some of the internal components of the watercraft10are shown in phantom while others are omitted for clarity. Fuel from the fuel tank14can be delivered to the engine15. The illustrated fuel tank14is placed at a forward location in a bottom portion of the body11. An oil tank16preferably is positioned rearwardly of the engine15. The oil tank16stores lubricant oil that is delivered to the engine15. The fuel tank14and the oil tank16can be at other locations based on the design of the engine compartment, engine design, and the like.

As shown inFIG. 2, the engine15preferably is a four cycle stroke, four cylinder engine. The engine15introduces a mixture of fuel and air through intake ports and discharges exhaust gases through exhaust ports. The mixture supplied into the engine15is combusted by an ignition of an ignition system (not shown) which is provided in the engine15. The flow of the air-fuel mixture is controlled by the intake valves and is ignited by an ignition device of the engine15. As such, the ignition device causes explosions that cause reciprocation of the pistons in the engine15. The reciprocal movement of the pistons drives a crankshaft15a.The crankshaft15ais coupled with an impeller shaft to transmit its rotational power to the impeller shaft to rotate it.

The illustrated engine merely exemplifies one type of engine which can have one or more embodiments of the present ground wire connecting structure. Engines having a different number of cylinders, other cylinder arrangements, various cylinder orientations (e.g., upright cylinder banks, V-type, and W-type), and operating on various combustion principles (e.g., four stroke, crankcase compression two-stroke, diesel, and rotary) are all practicable for use with the ground wire connecting structures disclosed herein.

With reference again toFIG. 1, a jet pump unit17is driven by the engine15to propel the illustrated watercraft10. An impeller shaft can extend between the crankshaft15aof the engine15and the jet pump unit17. A coupling member can be positioned between the impeller shaft and the crankshaft15a.The crankshaft15aimparts rotary motion to the impeller shaft which, in turn, drives the pump unit17.

The jet pump unit17is disposed within a tunnel formed on the underside of the lower hull section11b.The jet pump unit17preferably comprises a discharge nozzle and a steering nozzle to provide steering action. The steering nozzle is pivotally mounted about a generally vertical steering axis. The jet pump unit17can be connected to the handlebars12by a cable or other suitable arrangement so that a rider can pivot the steering nozzle for steering the watercraft10. Water introduced through the inlet of the jet pump unit17is discharged out from the water jet nozzle by the rotation of the impeller to propel the watercraft10. Other types of marine drives can also be used to propel the watercraft10depending upon the application.

With reference toFIG. 2, an intake system18comprises an intake conduit18a connected to the intake ports of the engine15. The intake system18also includes an intake box18cand a throttle device18bconnected to an upstream end of the intake conduit18a.The intake system18draws in outside ambient air through the intake box18cand then supplies the air to the engine15. A throttle valve of the throttle device18bselectively adjusts the amount of air delivered to the engine15. That is, the throttle valve can be opened and closed to accurately control the amount of air delivered to the engine15via the intake conduit18a.The fuel supplied from the fuel tank14through a fuel system14ais mixed with the air supplied to the engine15. The mixture is then ignited to drive the pistons of the engine15.

An exhaust system19includes an exhaust conduit19athat receives exhaust gases outputted from the engine15. The exhaust gases pass through the exhaust conduit19aand eventually to the outside environment. The exhaust system19preferably emits exhaust gases discharged from the engine15to an external location at a rear end portion of the body11.

The upstream end of the exhaust conduit19apreferably is in communication with the exhaust valves of the engine15. The exhaust conduit19aextends from each exhaust valve so that the exhaust gases from the combustion chambers of the engine15are mixed within and flow through the exhaust conduit19a.

With reference toFIGS. 1 and 2, a ground wire connecting structure20and/or associated oil tank16are positioned near the engine block of the engine15. The illustrated ground wire connecting structure20is disposed on a surface of the oil tank16positioned at the aft end of the engine15. Other positions of the ground wire connecting structure20and oil tank16are also possible. Additionally, the ground wire connecting structures can be mounted at other suitable locations of the watercraft.

With reference toFIGS. 3 and 4, the ground wire connecting structure20includes a joint unit22. A ground surface21a(seeFIGS. 5-7) is defined by the surface of the oil tank16. The ground surface21acan be a generally flat surface that extends along a portion of a surface of the oil tank16. The illustrated ground surface21ais an outwardly facing surface configured to mate with at least a portion of the joint unit22. The oil tank16can define ground surfaces of various configurations. Other body members, panels or surfaces of the watercraft10also can define a ground surface21athat engages at least a portion of the ground wire connecting structure20. One or more ground wire connecting structures can thus be mounted at various suitable locations in the watercraft10.

The joint unit22is preferably mounted to the ground surface21aso that the joint unit22is in electrical communication with the oil tank16. For example, the ground surface21ais preferably defined by one or more surfaces of an attachment support21that extends from the surface of the oil tank16. In the illustrated configuration, the attachment support21has a centrally disposed recess21b.A marginal area of the ground surface21ahas three threaded holes21c(only one is shown). As such, two ground surfaces21aare spaced apart from each other on either side of the recess21b.The oil tank16is preferably comprised of aluminum and/or its alloys, or any other suitable material.

The joint unit22includes a joint unit body or base body22a.The joint unit22is preferably constructed of aluminum and/or its alloy. In some embodiments, the joint unit22and the oil tank16are made of the same material (e.g., the same aluminum alloy). The attachment support21and the joint unit22thus can have similar physical properties (e.g., electrical properties including electrical conductivity). It should be appreciated that the joint body22and oil tank16can be formed from a plurality of materials. However, the mating surfaces (e.g., the ground surface21aand the contact portion23) can have similar properties, and preferably are comprised of similar or identical materials (e.g., the same metallic material). The ground wire connecting structure20can comprise a plurality of materials. For example, the joint body22and oil tank16can comprise metal, while the pair of connector sections22b(FIG. 5),22c(FIG. 6) is preferably made of another material.

As shown inFIGS. 8 and 9, the base body22aincludes a somewhat flat contact portion23that is in surface contact with the ground surface21aof the oil tank16. As shown inFIG. 5, the contact portion23engages the ground surface21a.The contact portion23preferably defines a contact surface23bfor mating with the ground surface21a.Through-hole forming portions24,25,26each include at least one through-hole. The illustrated base body22ahas three threaded holes21cformed in the contact portion23. The base body22aalso includes an attachment portion27(FIG. 9). Conductive members28a,28b(seeFIGS. 5 and 6) are attached to the attachment portion27as shown inFIG. 4. The illustrated conductive members28a,28bare in the form of bus bars, although the conductive members can have other designs.

A back side (i.e., the side opposing the ground surface21a) of the flat portion23is generally shaped as a trapezoidal structure in the illustrated configuration. The illustrated base side has a generally elliptically shaped annular groove23aas shown inFIG. 8. The groove23acan have various axial cross-sectional profiles. Non-limiting exemplary grooves can have semi-circular, polygonal, curved, or other suitable axial cross-sectional configurations based on the intended application. The groove23ais in a center portion of the contact portion23positioned along the longitudinal axis of the base body22a.However, the groove23acan be disposed at other locations. The groove23ais preferably positioned such that it is aligned with the attachment support21of the oil tank16. In such embodiments, the groove23acan cooperate with a sealing member to enhance the connection between the ground wire connecting structure20.

The contact surface23bis surrounded by the groove23a.The contact portion23is configured to contact the oil tank16(seeFIG. 8). The roughness (e.g., the degree of surface roughness) of both the contact portion23and the ground surface21acan be Ra 3.2 μm or higher. The flatness thereof can be about 0.1 mm. As such, a sufficient conductivity between the contact portion23and the ground surface21acan be provided. The surface properties of the contact portion23and the ground surface21acan be selected to achieve the desired connection (e.g., electrical connection) between the contact portion23and the ground surface21a.Roughness, flatness, electrical conductivity, and other surface properties can be selected on the intended application.

The contact area between the contact surface23bof the joint unit body22aand the ground surface21ais preferably equal to or greater than a cross-sectional area of one or more ground terminals. Current flowing from an external source (e.g., a ground wire) can effectively flow to the ground surface21a.The connection between the contact portion23of the joint unit body22aand the ground surface21acan be selected based on the roughness of the contact surface of the contact portion32band the ground surface21a.When the roughness of the surfaces is increased, the contact area between the contact surface23band the ground surface21acan be reduced. Accordingly, the area of the contact surface23band the ground surface21acan be increased to achieve a suitable electrical connection between the joint unit body22aand the oil tank16. In some embodiments, an effective contact area between the contact portion23of the joint unit body22aand the ground surface21acan be equal to or greater than the cross-sectional area of at least one ground terminal, although other configurations are possible.

With reference toFIG. 8, a sealing member29can cooperate with the groove23ato effectively from a seal between the base body22aand the oil tank16. The sealing member29is preferably an O-ring made of a rubber material and is configured to fit in the groove23a.An inner peripheral edge of the groove23ahas four anti-slip ribs23cspaced apart from each other to inhibit movement of the O-ring29. That is, the anti-slip ribs can secure the O-ring29in the groove23a.Preferably the O-ring29does not slip out of the groove23aor move a substantial distance during operation. Various types and numbers of anti-slip structures can be employed to inhibit relative movement between the O-ring29and the groove32a.For example, ribs, protrusions, adhesives, texturing, serrations, spikes and other anti-slip structures can be employed. Alternatively, the groove23amay not have any anti-slip structures.

The through-hole forming portions24and25are preferably positioned at relatively thicker portions at opposing ends of the base body22a.As shown inFIGS. 3 and 8, the through-hole forming portion25is positioned at an upper-most end of the base body22a.The through-hole forming portion24is positioned at a lower-most end of the base body22a.The through-hole forming portion26is generally positioned at a center portion at one side of the base body22a.The through-hole forming portion26is proximate the side that is shorter than the other, wherein both sides extend in the longitudinal direction. The illustrated through-hole forming portion26is positioned generally midway along the base body in the vertical direction.

The through hole forming portions24,25,26have centrally disposed through holes24a,25a,26a,respectively. Each of the through holes24a,25a,26aextends from the front side to the back side of the base body22a.The illustrated through holes24a,25a,26acorrespond to the three threaded holes21c(FIG. 7). The threaded holes21care preferably formed in the connecting support22, or other portion of the oil tank16. The base body22aof the joint body22is coupled to the ground surface21aof the oil tank16by inserting bolts35athrough corresponding through holes24a,25a,26a. Bolts35aare then screwed into the threaded holes21cthereby securely coupling the base body22ato the connecting support21of the oil tank16.

The attachment portion27(FIG. 9) includes a projection extending outwardly from a front surface of the flat portion23. A peripheral wall27aextends from a peripheral edge of the projection to define an attachment recess27b.That is, the attachment recess27bis defined and surrounded by the peripheral wall27a.As shown inFIGS. 8 and 9, the attachment recess27bhas three threaded holes27cspaced apart from each other. Each of the threaded holes27ccan have the same diameter and the same depth, although the threaded holes27ccan also have different dimensions if desired. A skilled artisan can select the desired number of threaded holes27cto be employed.

A portion of the peripheral wall27ais positioned forward relative the watercraft10and has two upper and lower notches. As shown inFIGS. 5 and 6, the attachment portion27has engaging recesses27d,27eat positions corresponding to the notches. The connector sections22b,22care coupled to the notches of the peripheral wall27aand the engaging recesses27d,27e.

With respect toFIGS. 10-12, each connector section22b,22chas a somewhat rectangular shape. The illustrated connector sections22b,22chave axial cross-sectional profiles that are substantially rectangular, as shown inFIG. 11. The connector section22bcan be coupled to the engaging recess27dand to the upper notch of the peripheral wall27avia a fixing portion31a.The fixing portion31ais preferably positioned at a base end of the connector section22b.That is, one end of the connector section22bis mounted to the fixing portion31a.The connector section22cis connected to the engaging recess27eand to the lower notch of the peripheral wall27avia a fixing portion31b.The fixing portion31bis preferably positioned at a base end of the connector section22c.Each fixing portion31a,31bhas a somewhat annular body. The periphery of each fixing portion31a,31bhas an engaging groove32a,32b,respectively. In the illustrated embodiment, the engaging groove32aengages the engaging recess27dand the upper notch of the peripheral wall27ato fix the fixing portion31ato the base body22a.The engaging groove32bengages the engaging recess27eand the lower notch of the peripheral wall27ato fix the fixing portion31bto the base body22a.

With continued reference toFIGS. 10 and 11, the connector section22bhas a plurality of elongated protrusions33b.The illustrated connector section22bincludes a pair of protrusions33bin the form of ribs extending in the fore and aft direction along its front side and the back side. The ribs33bextend outwardly from the vertically extending walls of the connector section22b.The connector section22bcan have at least one rib33bextending in the fore and aft direction on the upper and lower horizontally extending walls. At least one projection34bextends outwardly from a portion of the front side of the connector section22b,preferably extending from between the projected ribs33b.

The connector section22cpreferably has a greater axial length than the connector section22b,as shown inFIG. 10. As shown inFIG. 11, the traverse dimension of the connector section22cis preferably less than the transverse dimension of the connector section22b.Thus, the width of the connector section22cis generally less than the width of the connector section22b.It should be appreciated that the connector sections22b,22ccan have other configurations based on the intended application and harness configurations.

The connector section22chas a pair of projected ribs33cextending in the fore and aft direction on its front and back sides. The connector section22calso preferably includes at least one projection34cprojecting from a portion of the front side of the connector section22c.The at least one projection34cis preferably positioned between the projected ribs33c.In the illustrated embodiment, a single projection extends from a corresponding connector section22b,22c.

With reference toFIG. 10, bus bars28a,28bare provided for electrical communication between the body22aand the connector sections22b,22c.The bus bar28ais preferably formed with a plurality of conductive plates. The bus bar28apreferably includes a pair of conductive plates stacked on each other. Two through holes for mounting can extend through the bus bar28a.A bolt35bcan be disposed through a corresponding through hole for mounting of the bus bar28to the joint body22. In the illustrated embodiment, the bus bar28ais mounted to the joint body22by a pair of bolts35b.A skilled artisan can select the number of bolts used to mount the bus bar28. The bolts35bcan be inserted into the through-holes, and then screwed into one of the threaded holes27cto fix the bus bar28ato the attachment recess27b.One of the conductive plates of the bus bar28apositioned on the back side of the connector section22bcan be bent towards the back side. The two conductive plates can extend forwardly with a substantially constant distance between each other. A plurality of ground terminals36acan extend laterally (preferably forwardly) from the side of the bus bar28a,as shown inFIG. 5.

The bus bar28bincludes at least one conductive plate formed with one through hole. As shown inFIG. 6, the bolt35bcan be positioned within the through hole and can be screwed down to a corresponding threaded hole27c.The bolt35bcan couple the bus bar28bto the attachment recess27b.One or more ground terminals36bextend laterally (preferably forwardly) from the bus bar28b.The illustrated bus bar28bincludes a single conductive plate and the associated ground terminal36b.

At least a portion of the joint unit body22acan be positioned between at least one of the bus bars and the ground surface21a.One or more flow paths can be defined by the joint body22a.A flow path is preferably defined between the bus bars28a,28band the ground surface21a.The flow path can be defined by the joint body22. As shown inFIG. 5, a flow path100extends between the bus bar28aand the ground surface21a.As such, current can flow between the bus bar28aand the ground surface21avia the joint body22. Similarly, the joint body22can define a flow path102between the bus bar28band the ground surface21a.

A resin material can form a layer37that surrounds at least a portion of the ground terminals and at least partially fills the attachment recess27b.At least a portion of the bus bars28a,28bare interposed between the layer37and the joint body22. The layer37can substantially prevent water or other contaminates from contacting the bus bars28a,28b.Other types of materials can be used to form the layer37or to otherwise protect the bus bars28a,28b.

The illustrated layer37is a sealing layer formed at a fixing portion31a,31b,where the bus bars are coupled to the joint unit body22a.The layer37can be formed by applying a molten resin material into the attachment recess27bover the bus-bars. The resin material solidifies thereby forming the sealing layer37. The layer37can also couple the bus bars to the joint unit body22a.Further, water or the like can be inhibited (preferably substantially prevented) from entering any space between the joint unit body22aand the ground surface21a,and also locations where the fixing member is attached.

The watercraft10can contain various electric equipment, such as an electric control unit (ECU)41(FIG. 2), an injection device, an electronically operated throttling device, ignition system, and other devices typically found in watercraft. These electrical components can be contained within the body11of the watercraft. As shown inFIGS. 2 and 3, wire harnesses42a,42bcan extend from one or more of these devices to the ground wire connecting structure20. Each wire harness is configured to provide electrical communication between one or more of these electrical components and the ground wire connection structure20. In some embodiments, the wire harness42acomprises a bundle of ground wires. Tips of the ground wires can be spaced apart from each other and can be connected to a connector section43a.The connector section43ais removably attached to the connector section22b.In some cases, the connector section43acan be attached to or detached from the connector section22bby moving the connector section43ain the fore and aft direction relative to the connector section22b.When the connector section43ais attached to the connector section22b,the ground wires of the wire harness42acan be divided and connected to the ground terminals36a,as shown inFIG. 5.

With respect toFIGS. 3 and 6, the wire harness42bis also configured to provide electrical communication between one or more of electrical components of the watercraft and the ground wire connection structure20. The illustrated wire harness42bcomprises a bundle of ground wires. The tips of the ground wires can be spaced apart from each other and are preferably coupled to a connector section43b.The connector section43bcan be attached to or detached from the connector section22cby moving the connector section43bin the fore and aft direction relative to the connector section22a.When the connector section43bis attached to the connector section22c,the ground wires of the wire harness42bcan be connected to the associated ground terminals36b.

Each connector section43a,43bcan have an engaging concavity that engages a corresponding projection34b,34c.The engaging cavities and the projections34b,34ccooperate to maintain the connections between the respective ground wires of the wire harness and the associated ground terminal.

In the illustrated embodiment, electrical devices of the watercraft10are connected to the wire harnesses42a,42b.As such, these electrical devices are in electrical communication with the oil tank16through the respective ground terminals36a,36b,bus bars28a,28b,and base body22a.Hence, currents can flow from one or more electrical devices to the oil tank16.

To operate the watercraft10, an operator can first turn on a switch proximate the steering handlebars12to start running the watercraft10. The operator steers the watercraft10by moving the steering handlebars12and operates a throttling member on a grip of the steering handlebars12to control vehicle speed.

During operation of the watercraft10, various electrical devices can be connected to the oil tank16through the ground wires of the wire harnesses42a,42band the ground wire connecting structure20. Currents can flow from these electrical devices to the oil tank16. In some embodiments, even if water enters the body11of the watercraft10, water is inhibited from entering the internal components of the ground wire connecting structure20. In such embodiments, the ground wire connecting structure20can be exposed to water without substantially affecting the conductivity between the ground wire connecting structure20and the oil tank16.

The O-ring29is provided around the contact area between the ground surface21aand the contact portion23of the base body22a.The O-ring29inhibits the passage of water between the contacting portion23band the body22a.Thus, a water tight seal can be formed to limit effectively the amount of water contacting the contact area23b.To form an effective seal, the O-ring29can be compressed between the base body22aand the ground surface21a.Further, the layer37effectively protects the joint unit22from water. That is, the layer37inhibits the passage of water into the attachment recess27bof the joint unit22. The layer37can also protect and prevent water from contacting the bus bars. A suitable electrical connection can be maintained so that the electrical devices of the watercraft10are grounded.

The base body22apreferably comprises a conductive material, such as aluminum and/or its alloys. Preferably, at least a portion of the base body22aengaging the bus bars28a,28bis constructed of aluminum or its alloys. The base body22aalso contacts the ground surface21a.The back side of the base body22ahas the contact portion23that can contact the ground surface21ato form a relatively large contact zone. The large contact zone provides enhanced conductivity. The contact area between the contact portion23of the base body22aand the ground surface21acan be equal to or greater than the total cross-sectional area of the ground terminals36a,36b.In some embodiments, the contact area between the contact portion23of the base body22aand the ground surface21ais preferably substantially greater than the total cross-sectional area of the ground terminals36a,36b.Currents flowing from the respective ground wires of the wire harnesses42a,42bcan be efficiently discharged to the ground surface21a.

The ground surface21aof the oil tank16has the three threaded holes21c.The marginal area of the contact portion23of the base body22ahas the three through holes24a,25a,26a.Bolts35acan be inserted into the through holes24a,25a,26aand are threadably coupled to the attachment support21. In this manner the base body22aand oil tank16are assembled. In the illustrated embodiment, the bolts35aare screwed into to the threaded holes27cto couple the base body22asecurely to the ground surface21a.As such, the base body22acan be held against the ground surface21a.Also, in some embodiments, the overall dimensions of the ground wire connecting structure20can be reduced. The base body22acan be large enough to receive the bus bars28a,28band the connector units22b,22c.The base body22acan thus be compactly formed and can contribute to miniaturizing the ground wire connecting structure20.

The base body22ahas the groove23athat surrounds the contact surface23b.The O-ring29cooperates with the groove23ato form a water tight seal between the base body22aand the oil tank16. The water or other contaminates are inhibited (preferably substantially prevented) from passing between the ground surface21aand the contact surface23bof the base body22a.As such, the ground surface21aof the oil tank16and the contact portion23of the base body22aform an effective electrical connection such that current can flow through the base body22ato the oil tank16without interference from contaminates. Oxidation of the ground surface21aand/or the base body22aby the water (e.g., seawater) can be substantially limited or prevented. Also, because both the oil tank16and the base body22aare made of the same metal (e.g., an aluminum alloy), the ground surface21aand the base body22acan have the same potential thereby minimizing electrolytic corrosion. In other words, the surfaces of the structure20and the oil tank16that contact each other can have a similar corrosion compatibility to reduce overall corrosion, thus maintaining effective conductivity between the ground surface21aand the base body22a.Accordingly, the working life of ground wire connecting structure can be improved.

The seal layer37can comprise resin material and is preferably disposed in the attachment recess27bof the joint unit22. Water (e.g., seawater or the like) is therefore prevented from soaking the bus bars28a,28band/or the bolts35b.The resin material can comprise any material suitable for encapsulating these components and contacting water if desired.

Various electrical devices are disposed in the central area of the body11. The ground surface21ais formed in the surface of the oil tank16that is positioned in the central area of the body11. The respective lengths of the wire harnesses42a,42bextending from the devices can be reduced, and the respective ground wires of the wire harnesses42a,42bcan be easily connected to the associated ground terminals36a,36bof the joint unit22. Hence, the overall size of the electrical system can be reduced. It should be appreciated that the oil tank16can be at other locations also.

The ground wire connecting structure20is provided in a watercraft10and configured to cooperate with a portion of the oil tank16. The oil tank16can be disposed proximate the engine15. The illustrated oil tank16inFIGS. 1 and 2is positioned behind an engine15. The engine15and the oil tank16can be generally positioned in the center of a body11of the watercraft10. As such, the length of the ground wires extending from various devices of the watercraft10to the structure20can be reduced. The compact design and position of the engine15and oil tank16can reduce the required length of the ground wires that provide communication to the ground wire connecting structure20. Additionally, the ground wires can be conveniently connected to the ground terminals of the joint unit for easy assembly.

The ground wire connecting structure20is not limited to the embodiment describe above, and can be properly varied. For example, although the attachment recess27bgenerally houses the seal layer37in the embodiment described above, other portions in the joint unit22and around it (preferably except for the connector sections22b,22c) can have such a seal layer. Hence, waterproofing can be further improved various portions of the ground wire connecting structure20can be encapsulated by a sealing material. In another alternative, some portions such as, for example, a border between the ground surface21aand the base body22acan have a seal layer. The seal layer can further prevent contaminants from interfering with the electrical connection between the structure20and the oil tank16. In view of the present disclosure, a skilled artisan will readily recognize that one or more sealing layers can be employed to properly form barriers for inhibiting the ingress of contaminates into the ground wire connecting structure20.

The oil tank16and the base body22aare preferably made of an aluminum alloy in the embodiment described above. However, metallic materials other than aluminum alloys can be employed. Also, other materials, even if not metallic materials, are applicable if they are somewhat conductive. The oil tank16and the base body22acan be made of different materials from each other. Also, the ground wire connecting structure20can be applied not only to the watercraft10but also to a wide variety of vehicles such as, for example, a motorcycle, a motorcar, snowmobile, etc. Further, the ground wire connecting structure20can be disposed at any surface that is the structure20can be disposed at other surfaces than the surface of the oil tank16. For example, the structure20can be mounted to a body panel, frame, engine component, or other suitable body member for mounting of the structure20.