Abstract:
An engine includes an engine body and a generator. The engine body has a stator bracket mounted to the cylinder block. The generator incorporates a rotor flywheel and an armature assembly consisting of armature legs. Various metal plates with high magnetic permeability make up the armature legs and are securely fastened in a radial manner to the similar plate made of aluminum. The stacked armature legs surround the crankshaft and are mounted to the stator bracket. The preferred heat conduction path travels from the armature legs through the aluminum plate on onto the stator bracket in order to improve the heat dissipation of the generator.

Description:
PRIORITY INFORMATION  
       [0001]    This application is based on and claims priority to Japanese Patent Application No. 2000-339505, filed Nov. 7, 2000, the entire contents of which is hereby expressly incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to a generator arrangement for an engine, and more particularly to an improved generator cooling arrangement for a watercraft engine.  
         DESCRIPTION OF THE RELATED ART  
         [0003]    Watercraft engines typically incorporate electrical generators. The generator rotor is rotated by the engine and the electricity produced is used to recharge the battery or to directly power the ignition system used to ignite the fuel/air mixture inside the cylinder of the engine. Due to the compact design and waterproofing of watercraft engines and the fact that the generator itself produces heat, dissipation of the heat within the generator is an ongoing concern in watercraft applications.  
           [0004]    U.S. Pat. No. 6,184,599 assigned to Sanshin Kogyo Kabushiki Kaisha describes improvements in cooling generators including the use of cooling jackets and heat transfer elements.  
         SUMMARY OF THE INVENTION  
         [0005]    The preferred embodiments of the present invention, while having a very compact and confined waterproof design, effectively and cost efficiently dissipate the heat created by the generator on an engine in a watercraft.  
           [0006]    The stator armature of the generator includes a stack of plates of iron or other material having a high magnetic permeability. The individual plates are insulated from each other by a suitable dielectric. In addition, the stack includes a plate of aluminum that has substantially the same length and width dimensions. The armature coil is then wound around the entire assembly of plural iron plates and the abutting aluminum plate such that the aluminum plate is an integral part of the armature. A generally circular stator mounting bracket is also formed of aluminum. One surface of this bracket directly abuts the engine block. The opposite surface of this bracket directly abuts the aluminum plate integral with the armature stator.  
           [0007]    The aluminum plate is thus strategically positioned between the stacked metal plates and the aluminum stator bracket in order to very effectively dissipate heat away from the metal plates of the stator. As a result, the heat produced by resistors heating of the armature coils is directly conducted from the coils and armature iron plates through the integral aluminum plate and the aluminum mounting bracket to the engine block. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of a preferred embodiment, which is intended to illustrate and not to limit the invention. The drawings comprise four figures.  
         [0009]    [0009]FIG. 1 is a side elevational view of an outboard motor configured in accordance with a preferred embodiment of the present invention. An associated watercraft is partially shown in section.  
         [0010]    [0010]FIG. 2 is a sectioned side view of a generator assembly.  
         [0011]    [0011]FIG. 3 is a top sectional view taken along line  3 - 3  of FIG. 2; and  
         [0012]    [0012]FIG. 4 is an enlarged view of a stator assembly configured in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     The Overall Construction  
       [0013]    With reference to FIG. 1 an overall construction of an outboard motor  30  that employs an internal combustion engine  32  configured in accordance with certain features, aspects and advantages of the present invention will be described. The engine  32  has particular utility in the context of a marine drive, such as the outboard motor  30  for instance, and thus is described in the context of an outboard motor. The engine  32 , however, can be used with other types of marine drives (i.e., inboard motors, inboard/outboard motors, etc.) and also certain land vehicles, which includes lawnmowers, motorcycles, go carts, all terrain vehicles and the like. Furthermore, the engine  32  can be used as a stationary engine for some applications that will become apparent to those of ordinary skill in the art.  
         [0014]    In the illustrated arrangement, the outboard motor  30  generally comprises a drive unit  34  and a bracket assembly  36 . The bracket assembly  36  supports the drive unit  34  on a transom  38  of an associated watercraft  40  and places a marine propulsion device in a submerged position with the watercraft  40  resting relative to a surface  42  of a body of water. The bracket assembly  36  comprises a swivel bracket  44 , a clamping bracket  46 , a steering shaft  48  and a pivot pin  50 .  
         [0015]    The steering shaft  48  typically extends through the swivel bracket  44  and is affixed to the drive unit  34  by top and bottom mount assemblies  52 . The steering shaft  48  is pivotally journaled for steering movement about a generally vertically extending steering axis defined within the swivel bracket  44 . The clamping bracket  46  comprises a pair of bracket arms that preferably are laterally spaced apart from each other and that are attached to the watercraft transom  38 .  
         [0016]    The pivot pin  50  completes a hinge coupling between the swivel bracket  44  and the clamping bracket  46 . The pivot pin  50  extends through the bracket arms so that the clamping bracket  46  supports the swivel bracket  44  for pivotal movement about a generally horizontally extending tilt axis defined by the pivot pin  50 . The drive unit  34  thus can be tilted or trimmed about the pivot pin  50 .  
         [0017]    As used through this description, the terms “forward,” “forwardly” and “front” mean at or to the side where the bracket assembly  36  is located, unless indicated otherwise or otherwise readily apparent from the context use. The arrow Fw of FIG. 1 indicates the forward direction. The terms “rear,” “reverse,” “backwardly” and “rearwardly” mean at or to the opposite side of the front side.  
         [0018]    A hydraulic tilt and trim adjustment system  56  is provided between the swivel bracket  44  and the clamping bracket  46  for tilt movement (raising or lowering) of the swivel bracket  44  and the drive unit  34  relative to the clamping bracket  46 . Otherwise, the outboard motor  30  can have a manually operated system for tilting the drive unit  34 . Typically, the term “tilt movement”, when used in a broad sense, comprises both a tilt movement and a trim adjustment movement.  
         [0019]    The illustrated drive unit  34  comprises a power head  58  and a housing unit  60 , which includes a driveshaft housing  62  and a lower unit  64 . The power head  58  is disposed atop the housing unit  60  and includes an internal combustion engine  32  that is positioned within a protective cowling assembly  66 , which preferably is made of plastic. In most arrangements, the protective cowling assembly  66  defines a generally closed cavity  68  in which the engine  32  is disposed. The engine, thus, is generally protected from environmental elements within the enclosure defined by the cowling assembly  66 .  
         [0020]    The protective cowling assembly  66  comprises a top cowling member  70  and a bottom cowling member  72 . The top cowling member  70  is detachably affixed to the bottom cowling member  72  by a coupling mechanism so that a user, operator, mechanic or repairperson can access the engine  32  for maintenance or for other purposes. In some arrangements, the top cowling member  70  is hingedly attached to the bottom member such that the top cowling member  70  can be pivoted away from the bottom cowling member for access to the engine. Preferably, such a pivoting allows the top cowling member to be pivoted about the rear end of the outboard motor, which facilitates access to the engine from within the associated watercraft  40 .  
         [0021]    The top cowling member  70  preferably has a rear intake opening  76  defined through an upper rear portion. A rear intake member with one or more air ducts is unitarily formed with or is affixed to the top cowling member  70 . The rear intake member, together with the upper rear portion of the top cowling member  70 , generally defines a rear air intake space. Ambient air is drawn into the closed cavity  68  via the rear intake opening  76  and the air ducts of the rear intake member as indicated by an arrow  78  of FIG. 1. Typically, the top cowling member  70  tapers in girth toward its top surface, which is in the general proximity of the air intake opening  76 . The taper helps to reduce the lateral dimension of the outboard motor, which helps to reduce the air drag on the watercraft during movement.  
         [0022]    The bottom cowling member  72  has an opening through which an upper portion of an exhaust guide member or support member  80  extends. The exhaust guide member  80  preferably is made of aluminum alloy and is affixed atop the driveshaft housing  62 . The bottom cowling member  72  and the exhaust guide member  80  together generally form a tray. The engine  32  is placed onto this tray and can be affixed to the exhaust guide member  80 . The exhaust guide member  80  also defines an exhaust discharge passage through which burnt charges (e.g., exhaust gases) from the engine  32  pass.  
         [0023]    The engine  32  in the illustrated embodiment operates on a four-cycle combustion principle. This type of engine, however, merely exemplifies one type of engine on which various aspects and features of the present invention can be suitably used. Preferably, the engine has at least two cylinder banks, which extend separately of each other. For instance, an engine having an opposing cylinder arrangement can use certain features of the present invention. Nevertheless, engines having other numbers of cylinders, having other cylinder arrangements (in-line, opposing, etc.), and operating on other combustion principles (e.g., crankcase compression two-stroke or rotary) also can employ various features, aspects and advantages of the present invention. In addition, the engine can be formed with separate cylinder bodies rather than a number of cylinder bores formed in a cylinder block. Regardless of the particular construction, the engine preferably comprises an engine body that includes at least one cylinder bore.  
         [0024]    A crankshaft  82  extends generally vertically through a cylinder block  84  and can be journaled for rotation about a rotational axis  86  by several bearing blocks. Connecting rods (not shown) couple the crankshaft  82  with the respective pistons (not shown) in any suitable manner. Thus, the reciprocal movement of the pistons (not shown) rotates the crankshaft  82 .  
         [0025]    Preferably, the cylinder block  84  is located at the forwardmost position of the engine  32 ; a cylinder head assembly  88  being disposed rearward from the cylinder block  84 . Generally, the cylinder block  84  (or individual cylinder bodies) and the cylinder head assembly  88  together define the engine  32 . Typically, at least these major engine assemblies  84  and  88  are substantially made of aluminum alloy. The aluminum alloy advantageously increases strength over cast iron while decreasing the weight of the engine  32 .  
         [0026]    The engine  32  will also typically include a cooling system, a lubrication system and other systems, mechanisms or devices other than the systems described above.  
         [0027]    With reference again to FIG. 1, the driveshaft housing  62  depends from the power head  58  to support a driveshaft  90  which is coupled with the crankshaft  82  and which extends generally vertically through the driveshaft housing  62 . The driveshaft  90  is journaled for rotation and is driven by the crankshaft  82 . The driveshaft housing  62  defines an internal section  92  of the exhaust system that leads the majority of exhaust gases to the lower unit  64 . The internal section  92  includes an idle discharge portion that is branched off from a main portion of the internal section  92  to discharge idle exhaust gases directly out to the atmosphere through a discharge port that is formed on a rear surface of the driveshaft housing  62  in idle speed of the engine  32 .  
         [0028]    The lower unit  64  depends from the driveshaft housing  62  and supports a propulsion shaft  94  that is driven by the driveshaft  90 . The propulsion shaft  94  extends generally horizontally through the lower unit  64  and is journaled for rotation. A propulsion device is attached to the propulsion shaft  94 . In the illustrated arrangement, the propulsion device is a propeller  96  that is affixed to an outer end of the propulsion shaft  94 . The propulsion device, however, can take the form of a dual counter-rotating system, a hydrodynamic jet, or any of a number of other suitable propulsion devices.  
       Electrical Generator  
       [0029]    A preferred embodiment of the improved electrical generator  98  is shown in FIGS. 2, 3, and  4 .  
         [0030]    A stator core  102  includes a plurality of radially extended armature legs  104 . These armature legs  104  are uniformly spaced in a circle and attached to an aluminum stator bracket  110 . Each of the armature legs is advantageously made up of a series of uniformly spaced plates  106  of iron or other material having a high magnetic permeability. Each plate may be insulated from its adjoining plates by a suitable dielectric to inhibit eddy currents.  
         [0031]    By high magnetic permeability is meant sufficient permeability to provide ample electrical current. Typically this magnetic permeability will be equal to or greater than the magnetic permeability of iron.  
         [0032]    A significant feature of the preferred embodiment of this invention is an efficient, dissipation of heat from the armature. As best shown in the enlarged view of FIG. 4, each armature leg  104  includes an aluminum heat conductive plate  108  having a high thermal conductivity abutted against the plate  106  that is closest to the armature stator bracket. Plate  108  has advantageously the same planar dimensions, i.e., length and width, as each of the iron plates  106 . However, the thickness of plate  108  may be greater or less then the plate  106  as determined by the heat conduction requirements.  
         [0033]    By high thermal conductivity is meant superior heat dissipation properties in order to transfer heat efficiently and effectively. Typically this thermal conductivity will be greater than the thermal conductivity of iron or iron alloys. The thermal conductivity of aluminum compared to iron and other metals can be referenced in Mark&#39;s Standard Handbook for Mechanical Engineers, page 4-60, table 1.  
         [0034]    Each of the armature legs further includes an electrical winding  112 , typically provided by a suitable number of turns of insulated wire  112 . This armature coil  112  is wound around both the stack of iron sheets  106  and the aluminum plate  108  such that the plate  108  is an integral part of the stator armature. As a result, plate  108  is close proximity to both the stack of iron sheets  106  and the coil  112 .  
         [0035]    Aluminum heat conductive plate  108  is advantageously mounted to the aluminum stator bracket  110  of a sufficient mass designed to very effectively dissipate the generated heat from the armature legs  104 .  
         [0036]    A cup shaped flywheel rotor  100  preferably protected by a generator cover  101  is positioned above atop the crankshaft  82  and is mounted for rotation with the crankshaft  82 . Various permanent magnets  114  are positioned around the circumference of the flywheel rotor  100  that induces by magnetic induction an electrical current through various general coils  112 . As well known in the art, this electrical current is used to charge the boat battery or batteries as well as the various electrical needs of the engine  32  and watercraft.  
         [0037]    Bolts  116  secure each of the armature legs  104  to the stator bracket  110 . The stator bracket  110  is mounted to a through hole  118  in the engine block  84  or stationary member  120  with bolts  122 . A bearing  124  that guides and supports the crankshaft  82  is mounted within the stator bracket  110 .  
         [0038]    The electrical resistance heating within the stator armature is transferred from the highly thermal conductive aluminum heat sink plates  108  within each of the armature legs  104  to the stator bracket  110 . Bracket  110  in turn directly abuts the engine block  84 . As a result, the armature legs  104  are maintained at a safe operating temperature. The alternate long-and-short dashed line shown in FIG. 4 illustrates the path of heat transfer from the armature legs  104  to the stator bracket  110 .  
         [0039]    The present invention successfully satisfies both the growing demand for a compact design as well as effective heat dissipation.  
         [0040]    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.