IL43541A - Die cast combined sheave and flywheel assembly and method for making it - Google Patents

Description

43541/2 Die cast combined sheave and flywheel aseembly and method for making it OUTBOARD MARINE CORPORATION 0, 41683 '43541/2 CROSS-REFERENCE TO RELATED APPLICA TOM This invention is related to the invention disclosed in U.S. Patent Specification Serial No. 3,830,112 issued on August 20, 1974 which disclosure is incorporated herein by reference.

BACKGROUND OF THE INVENTION . This invention relates to flywheels and, more particularly, to a combined sheave and flywheel assembly for an internal combustion engine and a method for making the same.

Flywheels for various engines, such as internal com¬ bustion engines employed i snowmobiles and the like, are typically fabricated by die casting. These flywheels usually include one or more integral electrical components which are cas in place. An example of such a component is a pole shoe and magnet assembly which cooperates with a charge coil during rotation of the flywheel to charge alternators in the engine electrical system. The magnet assembly must be precisely ^ located. Consequently, means are required to initially position the magnet assembly at the proper location within the die cavity and to physically restrain the magnet assembly against .movement during injection of the molten metal into the die cavity.

Heretofore, such means has typically consisted of one or more locator pins provided on a first die section and •one or more projections provided on a second die section for each magnet assembly. The magnet assembly, which includes mating locator holes, is slipped onto the locator pins with one side abutting a shoulder or stop provided on the locator pins to properly positioa the magnet assembly within the die cavity. When the die sections are moved to a casting position, the projections on the second die section abut the other side of the magnet assembly and cooperate with the locator pins to retain the magnet assembly in place during injection of the molten metal into the die cavity. The spaces occupied by the locator pins and the projections become holes or openings in both faces of the flywheel assembly.

In some applications, the presence of such holes or openings in the face of the flywheel assembly is unacceptable. For instance, the Specification of U.S. Patent No. 3,830,112 describes arranging a flywheel assembly in a manner so as also to act as the fixed sheave member for a variable speed, V-belt transmission. Holes or openings in the inclined, belt-driving surface of such a flywheel assembly can cause excessive wear to the transmission drive belt driven thereby.

SUMMARY OF THE INVENTION The invention provides a combined sheave and flywheel assembly formed by die casting and including a circular body having a smooth, imperforate, radially inclined surface adapted to drivingly engage a transmission drive belt and an electrical component integrally cast in the body.

The invention also provides a method for die casting a combined sheave and flywheel assembly including a radially inclined surface for driving a transmission belt and a cast-in-place electrical component whereby the electrical component is accurately held in a predetermined position within the casting die cavity during the injection of molten metal thereinto without forming a hole or opening in the inclined belt-driving surface. More specifically, the method includes the steps of providing separable first-.and. second die sections which cooperate to define a die cavity, providing the first die section with locator means for locating the electrical component at a predetermined position within the die cavity providing the second die section with a radially inclined face which defines a portion of the die cavity forming a radially-inclined, belt-driving surface on the flywheel assembly, and providing the electrical component with an integral retainer means which is removably engaged by the second die section and cooperates with the second die section and the locator means to restrain movement of the component during injection of a molten metal into the die cavity. The retainer means is cast in as an integral part of the flywheel assembly so that a hole or opening is not left in the inclined belt-driving surface of the flywheel assembly casting upon removal from the casting die.

In the broadest aspect, the method provided by the invention can be used to die cast a member including a component integrally cast therein and on which an imperforate outer surface is desired.

An object of the invention is to provide a method for die casting a member having opposing outer faces whereby a component is accurately held in place within the cavity and becomes cast in as an integral part of the member without forming openings or holes in at least one of the opposing faces.

Another object of this invention is to provide a combined sheave and flywheel assembly having a radially inclined surface adaptable for driving a transmission belt without causing excessive wear.

A further object of this invention is to provide a method for die casting a combined sheave and flywheel assembly having a radially inclined surface whereby a cast-in-place component is accurately held in a predetermined position within the die cavity without forming a hole or opening in the inclined surface.

Other objects, aspects and advantages of the invention will become apparent from the following detailed description and accompanying drawing.

Fig. 1 is a fragmentary, diagramma ic representa ion of the prior art method for die casting a flywheel assembly.

Fig. 2 is a perspective view of a prior art pole shoe and magnet assembly. : Fig. 3 is a fragmentary, diagrammatic representation of the method of this invention for die casting a combined sheave and flywheel assembly.

Fig. 4 is a perspective view of a pole shoe and magnet assembly embodied by the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining the invention in detail, it is to be understood that the invention is not limited in its applicn tion to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawing. The invention is capable of other embodiments and can.be practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

The prior art method illustrated in Fig. 1 employs a metallic casting mold or die 10 (shown fragmentarily) includ ing two separable mold or die sections 12 and 14 (both shown fragmentarily) which, when positioned adjacent to each other in a casting position as shown, cooperate to define a die cavity corresponding. to the desired configuration of the flywheel assembly casting 18 (shown fragmentarily). The flywheel assembly casting 18 is formed in a conventional manner by 1 forcing a molten metal,.such as an aluminun^base alloy, into the die cavity under the influence of mechanical or pneumatic pressure, cooling the molten metal to a hardened state, and then separating the die sections 12 and 14 to permit removal of the flywheel assembly casting 18 from the die 10.

. . During the casting step, one or more components, such as a plurality of equiangularly-spaced , alinco pole shoe and magnet assemblies 20 (one shown), are cast in place and become an integral part of the flywheel assembly casting 18. With the die sections 12 and 14 separated to afford access to the die cavity, each magnet assembly 20 is installed onto one or more locator pins 22 extending inwardly from the inner face 24 of the die section 12 into the die cavity. The locator pins 22 are appropriately' located on the die section 12 to provide the desired position and circumferential spacing for the magnet assemblies 20.

The magnet assemblies 20 can be of any conventional design. In the prior art construction illustrated in Figs. 1 and 2, the magnet assembly 20 includes a generally U-shaped, laminated shoe unit 26 which carries a permanent magnet 28.

The pole shoe unit laminations 30 are held together with a pair of rivets 32 and are arranged with a protuberance 33 which is machined off, after the casting is removed from the die 10, to provide an opening or gap in the pole shoe unit 26 between the poles of the magnet 28. Locator holes 34 are provided in the opposite ends of the pole shoe unit 26 for receiving the locator pins 22. The locator pins 22 and the locator holes 24 are arranged to prevent magnet assembly movement transverse to the direction of separation of the die sections; The locator ■ pins 22 includes a shoulder 36 which abuts one side 38 of the pole shoe unit 26 to locate the magnet assembly within the die cavity in the direction of separation of the die ■sections.

After installation of the magnet assemblies 20, the die sections 12 and 14 are moved adjacent to each other to a casting position. . One or more projections 40 (one shown) extending inwardly from the inner face 42 of die section 14 into the die cavity engages the other side 44 of the pole shoe unit 26 and cooperate with the locator- pins 22 to clamp the magnet assembly 20 against movement. The molten aluminum-base alloy is then forced into the die cavity to fill the unoccupied space therein.

Upon separating the die sections 12 and 14, the spaces occupied by the projections 40 and the locator pins 22 become holes or openings in the opposite faces of the flywheel assembly casting 18. As mentioned above, the openings or holes produced in the inclined surface 46 of the flywheel assembly casting 18 by the projections 40 are unacceptable in flywheel assemblies arranged to also act as the fixed sheave member for a variable speed, V-belt transmission.

In accordance with the invention, a method for die casting a flywheel assembly is provided whereby the components which are cast in place' to become an integral part of the holes o openings in the inclined belt-driving surface of the flywheel assembly. In the preferred method illustrated in Figs. 3 and 4 the casting die 50 (shown fragmentarily) includes a die section 52 (shown fragmentarily) which is arranged in the same manner as the die section 12 in Fig. 1 and a die section 54 (shown fragmentarily) which is arranged substantially in the same manner as the die section 14 in Fig. 1 except that the projections 40 are omitted. Also, the inner face 56 of the die section 54 is arranged to form a radially inclined surface 58 on the flywheel assembly casting 60 so that the flywheel assembly can be used as the fixed sheave for a variable speed V-belt transmission as described in the above-identified co-pending application. The die section 54 also includes a plurality of recesses 62 (one shown). As with the prior art method described above, a plurality of equi-angularly-spaced , alinco pole shoe and magnet assemblies 64 (one shown) are cast in place and become an integral part of the flywheel assembly casting 60. The magnet assembly 64 includes a laminated pole shoe unit 66 and a permanent magnet 68 which are arranged in substantially the same manner as in the magnet assembly illustrated in Figs. 1 and 2 except for the modifications described below.

In accordance with the invention, the magnet assembly' 64 includes a retainer means which is removably engaged by the die section 54 and cooperates with the die section 54 and the locator means or pins 22 to clamp the magnet assembly 64 against movement during the injection of the molten aluminum-base alloy into the die cavity. While various constructions can be used, in the construction illustrated in Figs. 3 and 4, the magnet assembly 64 includes one or more elonga ed rivets 70 fastened at one end to the opposite ends of the pole shoe unit 66. The rivets 70 include a shank portion 72 extending ·. towards the inner surface 56 of the die section 54 and an outer end portion 74 which is removably received in the recess 62 during the casting operation. In operation in accordance with the method of the invention, the magnet assemblies 64 are first installed relative to the die section 52 by employment of suitable locator means or pins 22 and the die sections 52 and 54 are moved adjacent to each other to a casting position.

The magnet assembly 64 is held in place during casting, by cooperation of the die section 54, the rivets 70 and the locator means or pins 22. During the casting step, the rivets 70 become cast in as an integral part of the flywheel casting assembly 60.

Thus, instead of holes or openings existing in the inclined belt-driving surface 58 of the flywheel casting 60, the rivet end portions' 74 extend a small distance beyond the inclined face 58. The inclined face 58 and extending end portions 74 are machined to provide a smooth driving surface for the transmission belt.

If desired, one or more of the rivets 70 can be arranged with the outer ends inclined so as to be flush with the inner surface 56 of the die section 54 and thereby eliminat machining down of the extending end portions. However, this alternate method requires precise tolerances and. orientation of the rivets to insure a smooth belt-driving surface and, therefore, is less advantageous.

If desired, the rivets 32 can be omitted "so long as two rivets 70 are employed. Alternately one rivet 70 and one rivet 32 can be employed. Further, if the locator pin 22 is of non-circular cross-section and is received in a mating hole in the pole shoe unit, only one locator pin 22 can be used. , Still further, the locator means could include one or more recesses (such as the recesses 62) located in the die section 52 for cooperation with one or more rivets (such as the rivets 70) extending from the magnet assembly and located for insertion in such recesses in the die section 52. In such case one or more rivets would project from each side of the magnet assembly. If the projecting pins or rivets are of non-circular cross section and are receivable in mating recesses or holes, only one such pin a rivet could be used on each side. Additionally, only one such pin or rivet can be used if the component otherwise engages one of the die sections to assist in preventing movement thereof during casting.

The method provided by the invention is not limited to making a combined sheave and flywheel assembly as described in detail above. The method is broadly adaptable to die casting any member including a cast- in component which must be held in place within the die cavity during casting and wherein at least one imperforate surface on the die cast member is desired.

Various of the features of the irtvention are set forth in the following claims: Docket No. 2203 (E-639) 43541/2

Claims (7)

1. .1. A die cast combined sheave and flywheel assembly including a circular body having a smooth, imperforate,^ radially-inclined surface adapted to drivingly engage a transmission drive belt, and a component integrally cast into said body, said component having a retainer member which extends through said,body characterized in that said retainer member includes an outer end portion which is flush with said inclined surface.

2. A die cast combined sheave and flywheel assembly in accordance with Claim 1, wherein said component is a pole shoe and magnet. assembly including a generally'U-shaped , laminated pole " shoe unit, a permanent magnet carried' by said pole shoe unit, a locator opening in said pole shoe unit, adapted to receive a locator pin on a first section of a casting die, and rivet means fastened to said pole shoe unit characterized in that said rivet means is elongated and has an outer end portion adapted to be engaged by a second section of said -casting die and to cooperate with said second die casting section and said locator pin to thereby restrain movement of said assembly during casting. 43541/2

3. A method for making a flywheel assembly with a radially inclined belt-driving surface, which method comprises providing a component, providing a casting die including first and second separable die sections which, when moved relative to each other to a casting position, cooperate to define at least a portion of a die cavity corresponding to the desired configuration of the flywheel assembly, providing the first die section with a means for locating the component at a predetermined location located wholly within the die cavity and occupying a portion thereof so as to be cast in place integrally with the flywheel assembly, arranging the second die section with a radially inclined inner face which defines a portion of ..the die cavity forming the radially inclined, belt-driving surface on the . flywheel assembly, installing the component on the locating means, moving the die sections to the cas-ting position to form the die cavity independently of the component and so as, in cooperation with the locating means, to restrain movement of the component within the die cavity, filling the unoccupied portion of the die cavity with a molten metal, and cooling the molten metal to form the flywheel assembly with the component becoming < an integral part of the thus -formed flywheel assembly, characterized in that the step o providing the component includes providing a projection which extends, .'when the component is located at the predetermined position and the first and second die sections are in the casting position, through the die cavity towards the second die 43541/2 and in that, the step of moving the die sections to the casting position includes removably engaging the outer end portion of the projection with the inner face of the second die section so that, upon filling of the die cavity with molten metal, the belt-driving surface of the flywheel assembly is cast without a recess.

4. A method according to Claim 3 characterized in that the second die section includes a recess , wherein' the outer end portion of the projection extends for receipt into the recess, and further including the step of receiving the end portion of the projection into the recess when the die sections are moved to the casting position.

5. A method according to Claim " including removing the end portion of the projection to thereby provide a smooth, imperforate, radially inclined belt-driving surface-.

6. A method according to Claim 3 wherein the component is a pole shoe and magnet assembly including a pole shoe unit, a permanent magnet, and a rivet means fastened to the pole shoe unit, characterized in that the rivet means includes the projection. 43541/2 4

7. A method of die casting a flywheel assembly utilizing a casting die including first and second separable die sections which, when moved relative to each other to a casting position, cooperate to define at least a portion of a die cavity corresponding to the desired configuration of the flywheel assembly, and wherein the first die section includes means for locat ng, at a predetermined location within the die cavity, a component located wholly within the die cavity and occupying a portion thereof so as to be cast in place integrally with the flywheel assembly, wherein the second die section includes an inner face which defines a portion of the die cavity forming an outer surface of the flywheel assembly, and wherein the component includes a projection, said method comprising the steps of installing the component on the locating means, moving the die sections . to the. casting position so as to ... form the die cavity independently of the component and so as, in cooperation with the locating means, to restrain movement of the component within the die cavity, filling the unoccupied portion of the die cavity with ^ molten metal, and cooling the molten metal to form the flywheel assembly with the component including the projection becoming a non-removable part of the thus formed member, characterized in that the projection extends, when the component is located at the predetermined location and the first and second-die sections are in the casting position, through the die cavit . towards the second die section and has an outer end portion adapted to removably engage the inner face of the second die section and in that the step of moving the die sections to the casting position includes removably engaging the outer end portion of the projection with the inner face of the second die section so that, upon filling of the die